Monoclonal antibodies for treatment of cancer

ABSTRACT

The present invention provides antibodies useful as therapeutics for treating and/or preventing diseases associated with cells expressing GT468, including tumor-related diseases such as breast cancer, lung cancer, gastric cancer, ovarian cancer, and hepatocellular cancer.

RELATED APPLICATIONS

The present application is a divisional application of U.S. Ser. No.12/531,267 filed Sep. 14, 2009, which was a filed pursuant to 35 U.S.C.§371 as a U.S. National Phase application of International PatentApplication No. PCT/EP08/02063, which was filed Mar. 14, 2008, claimingthe benefit of priority to European Patent Application No. 07 005 258.4,filed on Mar. 14, 2007, and U.S. Patent Application No. 60/894,860,filed on Mar. 14, 2007. The entire text of the aforementionedapplications is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Antibody based cancer therapies have been successfully introduced intothe clinic and have emerged as the most promising therapeutics inoncology over the last decade.

Antibody-based therapies for cancer have the potential of higherspecificity and lower side effect profile as compared to conventionaldrugs. The reason is a precise distinction between normal and neoplasticcells by antibodies and the fact that their mode of action relies onless toxic immunological anti-tumor mechanisms, such as complementactivation and recruitment of cytotoxic immune cells.

Targets for antibody-based therapies need to have particular qualities,which form the basis for proper discrimination between normal andneoplastic cells. Obviously, a target with either exclusive restrictionto tumor cells and entirely undetectable on normal tissues is ideal forthe development of efficient and safe antibody therapeutics. In anotheraspect, a high-level overexpression may be the basis for the therapeuticwindow and low side effects exemplified by the human epidermal growthfactor receptor type 2 (HER-2), which as a result of gene amplificationis a good target for the antibody trastuzumab (Herceptin).

Other targets for antibodies which are either already approved or inclinical development for tumor therapy have distinct qualities, whichare not based on a numeric overexpression of target molecules on tumorcells. In the case of antibodies to the proteoglycan MUC-1, a peptiderepeat epitope in the backbone of the target is underglycosylated intumor cells and thus altered to its normal counterpart. In the case ofantibodies to CD20 (rituximab), CD52 (Campath-1H) and CD22(epratuzumab), antibody targets have comparable expression levels ontumor cells and normal lymphocytes. Here, the ablation of normal cellsby the antibody is tolerable since target-negative stem cells restorethe normal lymphocyte repertoire. Other examples of differentialaccessibility of antibody targets are carcinoembryonal antigen (CEA) andcarboanhydrase IX (CA9). Both antigens are expressed on normal epitheliaof colon and kidney, respectively. However, radioactively labeledimaging antibodies do distinguish well between tumor and normal tissue,and cytotoxic antibodies are well tolerated. This is most likely due toa restricted expression of CA9 and CEA on the luminal side of normalepithelial tissue when IgG antibodies do not have access. Also antigenepithelial cell adhesion molecule (Ep-CAM) belongs to this category. Asa homotypic cell adhesion molecule for epithelial cells it is localizedin the intercellular space. Intriguingly, whereas high-affinityanti-Ep-CAM antibodies are very toxic, intermediate-affinity antibodiesare well tolerated. This suggests accessibility of the Ep-CAM target onnormal cells but also indicates that kinetics of antibody binding mayopen a therapeutic window.

Eight antibodies have been approved for treatment of neoplasticdiseases, most of them, however in lymphoma and leukemia (Adams, G. P. &Weiner, L. M. (2005) Nat. Biotechnol. 23, 1147-1157). Only three mAbs,namely Herceptin, Avastin and Erbitux, address solid cancer types, whichaccount for more than 90% of cancer-evoked mortality. The substantialremaining medical need, the significant clinical benefit approved mAbshave already provided and their considerable commercial successaltogether motivated a wave of innovative approaches standing poised notonly to develop antibody-based therapies for extended groups of patientsbut also to improve their efficacy (Brekke, O. H. & Sandlie, I. (2003)Nat. Rev. Drug Discov. 2, 52-62; Carter, P. (2001) Nat. Rev. Cancer 1,118-129).

One of the challenges to be mastered for the advent of the nextgeneration of upgraded antibody-based cancer therapeutics is theselection of appropriate target molecules, which is the key for afavorable toxicity/efficacy profile.

Current antibodies available for the treatment of solid cancers owing tothe expression of their targets on normal tissues do not sufficientlyexploit the cumulative power of action modes embedded in antibodymolecules. Her2/neu, for instance, the target of Herceptin, is expressedin many normal human tissues including heart muscle (Crone, S. A., Zhao,Y. Y., Fan, L., Gu, Y., Minamisawa, S., Liu, Y., Peterson, K. L., Chen,J., Kahn, R., Condorelli, G. et al. (2002) Nat. Med. 8, 459-465). As aconsequence, Herceptin was designed with a reduced immunological potencyand cannot be given at the maximum effective dose, because of otherwiseunacceptable toxicity. This “blunting of a potentially sharp knife”limits the therapeutic efficacy of Herceptin.

In addition to lack of expression in toxicity relevant normal tissues,robust and high expression on the surface of tumor cells and exhibitionof a tumor promoting function are desirable characteristics for an idealantibody target (Houshmand, P. & Zlotnik, A. (2003) Curr. Opin. CellBiol. 15, 640-644).

Using an integrated data mining and experimental validation approach forthe discovery of new targets for antibody therapy of cancer weidentified GT468. GT468 is a placenta-specific gene with no detectableexpression in any other normal human tissue. However, it is frequentlyaberrantly activated and highly expressed in a variety of tumor types,in particular breast cancer. RNAi-mediated silencing of GT468 in MCF-7and BT-549 breast cancer cells profoundly impairs motility, migrationand invasion and induces a G1/S cell cycle block with nearly completeabrogation of proliferation. Knock down of GT468 is associated withdecreased expression of cyclin D1 and reduced phosphorylation of AKTkinase. Moreover, GT468 is localized on the surface of cancer cells andis accessible for antibodies which antagonize biological functions ofthis molecule.

GT468 has several properties that make it a highly attractive target fortherapeutic antibodies. Being a differentiation antigen of a celllineage which appears in the human body only in such an exceptionalstate as pregnancy, it is as absent from healthy toxicity-relevanttissues as a self-antigen can possibly be. Its high prevalence in avariety of tumor entities would make a broad number of patients eligiblefor treatment with GT468 targeting therapies. In the case of breastcancer for example, 82% of patients carry this target. Her2/neu, incontrast, the target of Herceptin, the only mAb available for treatmentof this cancer type, is overexpressed in only 20-25% of breast cancerpatients (Slamon, D. J., Godolphin, W., Jones, L. A., Holt, J. A., Wong,S. G., Keith, D. E., Levin, W. J., Stuart, S. G., Udove, J., Ullrich, A.et al. (1989) Science 244, 707-712). For lung cancer and for gastriccancer, in which GT468 is expressed in 42 and 58% of the casesrespectively, there is no approved mAB treatment so far owing to thelack of appropriate targets in these cancer types.

GT468 is druggable by antibodies on living cells and such antibodies mayprecipitate anti-tumoral effects such as proliferation inhibition. GT468is involved not only in proliferation but also cell motility, migrationand invasion. Most interestingly, all these attributes do not onlysubstantially contribute to the tumor phenotype but are also inherentproperties of the human trophoblast, which physiological characteristicsare to grow fast and to invade efficiently into uterus tissue. It isexpected that mAbs against GT468 can be engineered, which intervene withall these functions at once on top of their potential to mediate immuneeffector functions such as ADCC and CDC.

SUMMARY OF THE INVENTION

The present invention generally provides antibodies useful astherapeutics for treating and/or preventing diseases associated withcells expressing GT468 and/or being characterized by association ofGT468 with their cell surface, including tumor-related diseases such ascancer, in particular breast cancer, lung cancer, gastric cancer,ovarian cancer, hepatocellular cancer, colon cancer, pancreatic cancer,esophageal cancer, head & neck cancer, kidney cancer, prostate cancerand liver cancer.

In one aspect the invention relates to an antibody having the ability ofbinding to GT468. Preferably, the antibody has the ability of binding toGT468 located on the cell surface and preferably binds to one or moreepitopes located within the extracellular domain of GT468, preferablywithin amino acid residues 23-212 of GT468, and most preferably binds toan epitope located within one of the amino acid sequences of SEQ ID Nos:3-10 and 35-79. In one preferred embodiment, the antibody is specificfor one or more of the amino acid sequences of SEQ ID Nos: 3-10 and35-79. In various embodiments, the antibody has the ability of bindingto a peptide comprising amino acids 29 to 119, preferably amino acids 29to 212 and more preferably amino acids 23 to 212 of SEQ ID NO: 2.Preferably, the antibody binds to cancer cells, in particular cells ofthe cancer types mentioned above and, preferably, does not bindsubstantially to non-cancerous cells. Preferably, binding of saidantibody to cells expressing GT468 and/or being characterized byassociation of GT468 with their cell surface such as cancer cellsmediates killing of said cells and/or inhibits one or more activities ofsuch cells such as motility, migration, invasion and proliferation.Preferably, the antibody mediates killing of said cells and/or inhibitsproliferation of said cells.

Killing of cells and/or inhibition of one or more activities of cells,in particular cell proliferation, by the antibody of the invention ispreferably induced by binding of the antibody to GT468 expressed by saidcells and/or being associated with the cell surface of said cells. Suchkilling of cells and/or inhibition of one or more activities of cellscan be utilized therapeutically as described herein. In particular,killing of cells and/or inhibition of proliferation of cells can beutilized for treating or preventing cancer. Inhibition of motility,migration, invasion and/or proliferation of cells can be utilized fortreating or preventing cancer, in particular cancer metastasis and themetastatic spread of cancer cells.

The cells expressing GT468 and/or being characterized by association ofGT468 with their cell surface are preferably cancer cells and are, inparticular, selected from the group consisting of tumorigenic breast,lung, gastric, ovarian, liver, colon, pancreatic, esophageal, head-neck,renal and prostate cancer cells.

Preferably the antibody of the invention mediates killing of cells byinducing complement dependent cytotoxicity (CDC) mediated lysis,antibody dependent cellular cytotoxicity (ADCC) mediated lysis,apoptosis, homotypic adhesion, and/or phagocytosis, preferably byinducing CDC mediated lysis and/or ADCC mediated lysis.

In one embodiment the antibody of the invention does not induce CDCmediated lysis of cells.

Preferably, ADCC mediated lysis of cells takes place in the presence ofeffector cells, which in particular embodiments are selected from thegroup consisting of monocytes, mononuclear cells, NK cells and PMNs, andphagocytosis is by macrophages.

The antibody of the invention may be a monoclonal, chimeric, human, orhumanized antibody, or a fragment of an antibody and may be selectedfrom the group consisting of an IgG1, an IgG2, preferably IgG2a andIgG2b, an IgG3, an IgG4, an IgM, an IgA1, an IgA2, a secretory IgA, anIgD, and an IgE antibody.

According to all aspects of the invention, GT468 is preferably humanGT468, preferably having the amino acid sequence according to SEQ ID NO:2, more preferably having the amino acid sequence of the extracellulardomain of the amino acid sequence according to SEQ ID NO: 2, inparticular having the amino acid sequence spanning from amino acids 23to 212 of SEQ ID NO: 2.

In particular preferred embodiments, the antibody of the invention bindsto native epitopes of GT468 present on the surface of living cells suchas those of SEQ ID NOs: 3-10 and 35-79. In further preferredembodiments, the antibody of the invention is specific for cancer cells,preferably breast cancer cells.

In certain embodiments of the invention, GT468 is expressed on and/orassociated with the surface of cells.

Antibodies of the invention may be obtained by a method comprising thestep of immunizing an animal with a protein or peptide having an aminoacid sequence selected from the group consisting of SEQ ID NOs: 2-10 and35-79, or an immunogenic fragment or derivative thereof, or a nucleicacid or host cell expressing said protein or peptide, or immunogenicfragment or derivative thereof. Preferably, an antibody of the inventionis specific for the afore mentioned proteins, peptides or immunogenicfragments or derivatives thereof. In the context of a protein or peptideused in immunization a derivative relates to a variant of such proteinor peptide which has the same immunogenic properties as the protein orpeptide from which it is derived. In particular, the derivative of aprotein or peptide when used in immunization for the production ofantibodies, in particular monoclonal antibodies, provides antibodieshaving the same specificity as antibodies obtained when using theprotein or peptide in immunization. For example, such derivative mayinclude the deletion, substitution or addition of one or more aminoacids. In particular, it may include the addition of one or more aminoacids such as cysteine at either the N-terminus or C-terminus or both.

In a particularly preferred embodiment, the antibody of the invention isproduced by a clone having the accession no. DSM ACC2822 (4E9-1H9), DSMACC2826 (9B6-2A9), DSM ACC2824 (59D6-2F2), DSM ACC2825 (61C11-2B5), DSMACC2823 (78H11-1H6), DSM ACC2895 (22-1A-1), DSM ACC2893 (22-2A-1), DSMACC2896 (22-9B-1), DSM ACC2897 (23-33A-1), DSM ACC 2891 (23-19A-1), DSMACCX2894 (F11#33F7D12), DSM ACC2892 (4A12 2D4 1A10), or DSM ACC2898 (4E91D12 2D4).

In one embodiment the antibody of the invention is coupled to atherapeutic agent such as a toxin, a radioisotope, a drug or a cytotoxicagent.

In a further aspect the invention relates to a hybridoma capable ofproducing the antibody of the invention. Preferred hybridomas are thosehaving the accession no. DSM ACC2822 (4E9-1H9), DSM ACC2826 (9B6-2A9),DSM ACC2824 (59D6-2F2), DSM ACC2825 (61C11-2B5), DSM ACC2823(78H11-1H6), DSM ACC2895 (22-1A-1), DSM ACC2893 (22-2A-1), DSM ACC2896(22-9B-1), DSM ACC2897 (23-33A-1), DSM ACC2891 (23-19A-1), DSM ACC2894(F11#33F7D12), DSM ACC2892 (4A12 2D4 1A10), or DSM ACC2898 (4E9 1D122D4).

Antibodies of the invention are designated herein by referring to thedesignation of the antibody and/or by referring to the clone producingthe antibody, e.g. 4E9-1H9.

The invention also relates to a pharmaceutical composition comprising anantibody of the invention and/or a conjugate thereof with a therapeuticagent, and a pharmaceutically acceptable carrier.

In a further aspect the invention relates to a method of inhibiting oneor more activities selected from motility, migration, invasion andgrowth, preferably growth and/or killing of a cell expressing GT468and/or being characterized by association of GT468 with its cellsurface, comprising contacting the cell with an effective amount of anantibody of the invention and/or a conjugate thereof with a therapeuticagent. GT468 is preferably expressed on the surface of said cell.

In a further aspect the invention relates to a method of treating orpreventing a disease or disorder involving cells expressing GT468 and/orbeing characterized by association of GT468 with their cell surfacecomprising administering to a subject an antibody of the invention, aconjugate thereof with a therapeutic agent, or a pharmaceuticalcomposition comprising the antibody of the invention or the conjugatethereof with a therapeutic agent. Preferably the disease or disorder isa tumor-related disease and in particular embodiments is selected fromthe group consisting of breast cancer, lung cancer, gastric cancer,ovarian cancer, hepatocellular cancer, colon cancer, pancreatic cancer,esophageal cancer, head & neck cancer, kidney cancer, prostate cancerand liver cancer. GT468 is preferably expressed on the surface of saidcells.

Preferably, the antibodies of the invention have the ability todiscriminate GT468-variants expressed by different cell types includingcancer cells and non-malignant cells.

The term “binding” according to the invention preferably relates to aspecific binding. “Specific binding” means that an agent such as anantibody binds stronger to a target such as an epitope for which it isspecific compared to the binding to another target. An agent bindsstronger to a first target compared to a second target if it binds tothe first target with a dissociation constant (K_(D)) which is lowerthan the dissociation constant for the second target. Preferably thedissociation constant (K_(D)) for the target to which the agent bindsspecifically is more than 10-fold, preferably more than 20-fold, morepreferably more than 50-fold, even more preferably more than 100-fold,200-fold, 500-fold or 1000-fold lower than the dissociation constant(K_(D)) for the target to which the agent does not bind specifically.

The antibodies of the invention preferably mediate killing of cellsexpressing GT468 and/or being characterized by association of GT468 withtheir cell surface by binding to GT468. Preferably GT468 is expressed onthe surface of said cells. In one embodiment, antibodies of theinvention induce complement dependent cytotoxicity (CDC), e.g. at leastabout 20-40% CDC mediated lysis, preferably about 40-50% CDC mediatedlysis, and more preferably more than 50% CDC mediated lysis of cellsexpressing GT468 and/or being characterized by association of GT468 withtheir cell surface. Alternatively or in addition to inducing CDC,antibodies of the invention may induce antibody dependent cellularcytotoxicity (ADCC) of cells expressing GT468 and/or being characterizedby association of GT468 with their cell surface in the presence ofeffector cells (e.g., monocytes, mononuclear cells, NK cells and PMNs).Antibodies of the invention may have the ability to induce apoptosis ofcells expressing GT468 and/or being characterized by association ofGT468 with their cell surface, induce homotypic adhesion of cellsexpressing GT468 and/or being characterized by association of GT468 withtheir cell surface and/or induce phagocytosis of cells expressing GT468and/or being characterized by association of GT468 with their cellsurface in the presence of macrophages. The antibodies of the inventionmay have one or more of the above described functional properties.Preferably, antibodies of the invention induce CDC mediated lysis andADCC mediated lysis of cells expressing GT468 and/or being characterizedby association of GT468 with their cell surface and more preferablyinduce ADCC mediated lysis of cells expressing GT468 and/or beingcharacterized by association of GT468 with their cell surface while theydo not induce CDC mediated lysis of said cells. Exemplary target cellsfor antibodies of the present invention include, but are not limited to,cancer cells expressing GT468 and/or being characterized by associationof GT468 with their cell surface such as tumorigenic breast, lung,gastric, ovarian and hepatocellular cancer cells. In a particularpreferred embodiment, killing of cells mediated by antibodies of theinvention is GT468 specific, i.e. antibodies of the invention mediatekilling, preferably CDC and/or ADCC mediated lysis, of cells expressingGT468 and/or being characterized by association of GT468 with their cellsurface but do not mediate killing of cells not expressing GT468 and/ornot being characterized by association of GT468 with their cell surface.The antibodies described above may be used to mediate killing of tumorcells in the treatment or prevention of cancer such as breast cancer,lung cancer, gastric cancer, ovarian cancer, hepatocellular cancer,colon cancer, pancreatic cancer, esophageal cancer, head & neck cancer,kidney cancer, prostate cancer and liver cancer.

Antibodies of the invention may be derived from different species,including but not limited to mouse, rat, rabbit, guinea pig and human.Antibodies of the invention also include chimeric molecules in which anantibody constant region derived from one species, preferably human, iscombined with the antigen binding site derived from another species.Moreover antibodies of the invention include humanized molecules inwhich the antigen binding sites of an antibody derived from a non-humanspecies are combined with constant and framework regions of humanorigin.

Antibodies of the invention include polyclonal and monoclonal antibodiesand include IgG2a (e.g. IgG2a, κ, λ), IgG2b (e.g. IgG2b, κ, λ), IgG3(e.g. IgG3, κ, λ) and IgM antibodies. However, other antibody isotypesare also encompassed by the invention, including IgG1, IgA1, IgA2,secretory IgA, IgD, and IgE antibodies. The antibodies can be wholeantibodies or antigen-binding fragments thereof including, for example,Fab, F(ab′)₂, Fv, single chain Fv fragments or bispecific antibodies.Furthermore, the antigen-binding fragments include binding-domainimmunoglobulin fusion proteins comprising (i) a binding domainpolypeptide (such as a heavy chain variable region or a light chainvariable region) that is fused to an immunoglobulin hinge regionpolypeptide, (ii) an immunoglobulin heavy chain CH2 constant regionfused to the hinge region, and (iii) an immunoglobulin heavy chain CH3constant region fused to the CH2 constant region. Such binding-domainimmunoglobulin fusion proteins are further disclosed in US2003/0118592and US 2003/0133939.

Antibodies of the present invention preferably dissociate from GT468with a dissociation equilibrium constant (KD) of approximately 1-100 nMor less. Preferably, antibodies of the invention do not cross-react withrelated cell-surface antigens and thus do not inhibit their function.

In preferred embodiments, antibodies of the present invention can becharacterized by one or more of the following properties:

-   -   a) specificity for GT468;    -   b) a binding affinity to GT468 of about 100 nM or less,        preferably, about 5-10 nM or less and, more preferably, about        1-3 nM or less,    -   c) the ability to mediate a high level of CDC on either CD55/59        negative or CD55/59 positive cells;    -   d) the ability to inhibit the growth of cells which express        GT468 and/or are characterized by association of GT468 with        their cell surface;    -   e) the ability to induce apoptosis of cells which express GT468        and/or are characterized by association of GT468 with their cell        surface;    -   f) the ability to induce homotypic adhesion of cells which        express GT468 and/or are characterized by association of GT468        with their cell surface;    -   g) the ability to induce ADCC of cells which express GT468        and/or are characterized by association of GT468 with their cell        surface in the presence of effector cells;    -   h) the ability to prolong survival of a subject having tumor        cells which express GT468 and/or are characterized by        association of GT468 with their cell surface;    -   i) the ability to deplete cells which express GT468 and/or are        characterized by association of GT468 with their cell surface;    -   j) the ability to deplete cells which express low levels of        GT468 and/or are characterized by association of GT468 with        their cell surface and/or    -   k) the ability to aggregate GT468 on the surface of living cells

The anti-GT468 antibodies of the present invention can be derivatized,linked to or co-expressed to other binding specificities. In aparticular embodiment, the invention provides a bispecific ormultispecific molecule comprising at least one first binding specificityfor GT468 (e.g., an anti-GT468 antibody or mimetic thereof), and asecond binding specificity for a effector cell, such as a bindingspecificity for an Fc receptor (e.g., a Fc-gamma receptor, such asFc-gamma RI, or any other Fc receptor) or a T cell receptor, e.g., CD3.

Accordingly, the present invention includes bispecific and multispecificmolecules that bind to both GT468 and to an Fc receptor or a T cellreceptor, e.g. CD3. Examples of Fc receptors are IgG receptor, Fc-gammareceptor (FcγR), such as FcγRI (CD64), FcγRII (CD32), and FcγRIII(CD16). Other Fc receptors, such as IgA receptors (e.g., FcαRI), alsocan be targeted. The Fc receptor is preferably located on the surface ofan effector cell, e.g., a monocyte, macrophage or an activatedmononuclear cell. In a preferred embodiment, the bispecific andmultispecific molecules bind to an Fc receptor at a site which isdistinct from the immunoglobulin Fc (e.g., IgG or IgA) binding site ofthe receptor. Therefore, the binding of the bispecific and multispecificmolecules is not blocked by physiological levels of immunoglobulins.

In yet another aspect, anti-GT468 antibodies of the invention arederivatized, linked to or co-expressed with another functional molecule,e.g., another peptide or protein (e.g., a Fab′ fragment). For example,an antibody of the invention can be functionally linked (e.g., bychemical coupling, genetic fusion, noncovalent association or otherwise)to one or more other molecular entities, such as another antibody (e.g.to produce a bispecific or a multispecific antibody), a cytotoxin,cellular ligand or antigen (e.g. to produce an immunoconjugate, such asan immunotoxin). An antibody of the present invention can be linked toother therapeutic moieties, e.g., a radioisotope, a small moleculeanti-cancer drug, a recombinant cytokine or chemokine. Accordingly, thepresent invention encompasses a large variety of antibody conjugates,bispecific and multispecific molecules, and fusion proteins, all ofwhich bind to GT468 expressing cells and/or to cells being characterizedby association of GT468 with their cell surface and which can be used totarget other molecules to such cells.

In a further aspect, the invention also envisions GT468-binding proteinsderived from non-immunoglobulin domains, in particular single-chainproteins. Such binding proteins and methods for their production aredescribed, for example, in Binz et al. (2005) Nature Biotechnology 23(10): 1257-1268, herein incorporated by reference. It is to beunderstood that the teaching given herein with respect to immunoglobulinor immunoglobulin derived binding molecules correspondingly also appliesto binding molecules derived from non-immunoglobulin domains. Inparticular, using such binding molecules derived from non-immunoglobulindomains it is possible to block GT468 of cells expressing said targetand/or being characterized by association of said target with their cellsurface and thus, to bring about therapeutic effects as disclosed hereinfor antibodies of the invention, in particular the inhibition of one ormore activities of tumor cells as disclosed herein such asproliferation. Although not mandatory, it is possible to confer effectorfunctions of antibodies to such non-immunoglobulin binding molecules bye.g. fusion to the Fc region of antibodies.

In still another aspect, the invention provides compositions, e.g.,pharmaceutical and diagnostic compositions/kits, comprising apharmaceutically acceptable carrier formulated along with one or acombination of antibodies of the invention. In a particular embodiment,the composition includes a combination of antibodies which bind todistinct epitopes or which possess distinct functional characteristics,such as inducing CDC and/or ADCC and inducing apoptosis. In thisembodiment of the invention, antibodies may be used in combination,e.g., as a pharmaceutical composition comprising two or more anti-GT468monoclonal antibodies. For example, anti-GT468 antibodies havingdifferent but complementary activities can be combined in a singletherapy to achieve a desired therapeutic effect. In a preferredembodiment, the composition includes an anti-GT468 antibody thatmediates CDC combined with another anti-GT468 antibody that inducesapoptosis. In another embodiment, the composition includes an anti-GT468antibody that mediates highly effective killing of target cells in thepresence of effector cells, combined with another anti-GT468 antibodythat inhibits the growth of cells expressing GT468 and/or beingcharacterized by association of GT468 with their cell surface.

The present invention also includes the simultaneous or sequentialadministration of two or more anti-GT468 antibodies of the invention,wherein preferably at least one of said antibodies is a chimericanti-GT468 antibody and at least one further antibody is a humananti-GT468 antibody, the antibodies binding to the same or differentepitopes of GT468. Preferably, a chimeric GT468 antibody of theinvention is administered first followed by the administration of ahuman anti-GT468 antibody of the invention, wherein the human anti-GT468antibody is preferably administered for an extended period of time, i.e.as maintenance therapy.

Antibodies, immunoconjugates, bispecific and multispecific molecules andcompositions of the present invention can be used in a variety ofmethods for inhibiting growth of cells expressing GT468 and/or beingcharacterized by association of GT468 with their cell surface and/orselectively killing cells expressing GT468 and/or being characterized byassociation of GT468 with their cell surface by contacting the cellswith an effective amount of the antibody, immunoconjugate,bispecific/multispecific molecule or composition, such that the growthof the cell is inhibited and/or the cell is killed. In one embodiment,the method includes killing of the cell expressing GT468 and/or beingcharacterized by association of GT468 with their cell surface,optionally in the presence of effector cells, for example, by CDC,apoptosis, ADCC, phagocytosis, or by a combination of two or more ofthese mechanisms. Cells expressing GT468 and/or being characterized byassociation of GT468 with their cell surface which can be inhibited orkilled using the antibodies of the invention include cancer cells suchas breast, lung, gastric, ovarian, liver, colon, pancreatic, esophageal,head & neck, kidney, prostate and liver cells.

Accordingly, antibodies of the present invention can be used to treatand/or prevent a variety of diseases involving cells expressing GT468and/or being characterized by association of GT468 with their cellsurface by administering the antibodies to patients suffering from suchdiseases. Exemplary diseases that can be treated (e.g., ameliorated) orprevented include, but are not limited to, tumorigenic diseases.Examples of tumorigenic diseases, which can be treated and/or prevented,include breast cancer, lung cancer, gastric cancer, ovarian cancer,hepatocellular cancer, colon cancer, pancreatic cancer, esophagealcancer, head & neck cancer, kidney cancer, prostate cancer and livercancer.

In a particular embodiment of the invention, the subject beingadministered the antibody is additionally treated with achemotherapeutic agent, radiation, or an agent that modulates, e.g.,enhances or inhibits, the expression or activity of an Fc receptor, e.g.an Fc-gamma receptor, such as a cytokine. Typical cytokines foradministration during treatment include granulocyte colony-stimulatingfactor (G-CSF), granulocyte-macrophage colony-stimulating factor(GM-CSF), interferon-γ (IFN-γ), and tumor necrosis factor (TNF). Typicaltherapeutic agents include, among others, anti-neoplastic agents such asdoxorubicin, cisplatin, taxotere, 5-fluoruracil, methotrexate,gemzitabin and cyclophosphamide.

In yet another aspect, the invention relates to an immunization strategyto immunize non-human animals such as mice with human GT468 or a peptidefragment thereof to obtain antibodies. Preferred peptides forimmunization are those selected from the group consisting of SEQ ID NO:2-10 and 35-79, or derivatives thereof. Accordingly, in preferredembodiments, the antibodies of the invention are those obtained byimmunization using peptides selected from the group consisting of SEQ IDNO: 2-10 and 35-79, or derivatives thereof. Analogously, antibodies toGT468 can be generated in a transgenic non-human animal, such as atransgenic mouse. The transgenic non-human animal may be a transgenicmouse having a genome comprising a heavy chain transgene and a lightchain transgene encoding all or a portion of an antibody.

Wildtype as well as transgenic non-human animals can be immunized with apurified or enriched preparation of GT468 antigen and/or nucleic acidsand/or cells expressing GT468 or a peptide fragment thereof. Preferably,the non-human animal is capable of producing multiple isotypes of humanmonoclonal antibodies to GT468 (e.g., IgG, IgA and/or IgM) by undergoingV-D-J recombination and isotype switching. Isotype switching may occurby e.g., classical or non-classical isotype switching.

Accordingly, in yet another aspect, the invention provides isolated Bcells from a non-human animal as described above. The isolated B cellscan then be immortalized by fusion to an immortalized cell to provide asource (e.g., a hybridoma) of antibodies of the invention. Suchhybridomas (i.e., which produce antibodies of the invention) are alsoincluded within the scope of the invention.

As exemplified herein, antibodies of the invention can be obtaineddirectly from hybridomas which express the antibody, or can be clonedand recombinantly expressed in a host cell (e.g., a CHO cell, or alymphocytic cell). Further examples of host cells are microorganisms,such as E. coli, and fungi, such as yeast. Alternatively, they can beproduced recombinantly in a transgenic non-human animal or plant.

Preferred hybridoma cells for producing antibodies of the invention arethose deposited at the DSMZ (Inhoffenstr. 7B, 38124 Braunschweig,Germany) having the following designations and accession numbers:

a) 4E9-1H9, accession no. DSM ACC2822, deposited on Mar. 13, 2007

b) 9B6-2A9, accession no. DSM ACC2826, deposited on Mar. 13, 2007

c) 59D6-2F2, accession no. DSM ACC2824, deposited on Mar. 13, 2007

d) 61C11-2B5, accession no. DSM ACC2825, deposited on Mar. 13, 2007

e) 78H11-1H6, accession no. DSM ACC2823, deposited on Mar. 13, 2007

f) 22-1A-1, accession no. DSM ACC2895, deposited on Mar. 11, 2008

g) 22-2A-1, accession no. DSM ACC2893, deposited on Mar. 11, 2008

h) 22-9B-1, accession no. DSM ACC2896, deposited on Mar. 11, 2008

i) 23-33A-1, accession no. DSM ACC2897, deposited on Mar. 11, 2008

j) 23-19A-1, accession no. DSM ACC2891, deposited on Mar. 11, 2008

k) F11#33F7D12, accession no. DSM ACC2894 deposited on Mar. 11, 2008

l) 4AI2 2D4 1A1 0, accession no. DSM ACC2892, deposited on Mar. 11, 2008

m) 4E9 1D12 2D4, accession no. DSM ACC2898, deposited on Mar. 11, 2008

Preferred antibodies of the invention are those produced by andobtainable from the above-described hybridomas and the chimerized andhumanized forms thereof. Further preferred antibodies of the inventionare those having the specificity of the antibodies produced by andobtainable from the above-described hybridomas and, in particular, thosecomprising the antigen binding portion or antigen binding site, inparticular the variable region, of the antibodies produced by andobtainable from the above-described hybridomas.

In preferred embodiments, antibodies, in particular chimerised forms ofantibodies according to the invention include antibodies comprising aheavy chain constant region (CH) comprising an amino acid sequencederived from a human heavy chain constant region such as the amino acidsequence represented by SEQ ID NO: 17 or 24 or a fragment thereof. Infurther preferred embodiments, antibodies, in particular chimerisedforms of antibodies according to the invention include antibodiescomprising a light chain constant region (CL) comprising an amino acidsequence derived from a human light chain constant region such as theamino acid sequence represented by SEQ ID NO: 18 or 22 or a fragmentthereof. In a particular preferred embodiment, antibodies, in particularchimerised forms of antibodies according to the invention includeantibodies which comprise a CH comprising an amino acid sequence derivedfrom a human CH such as the amino acid sequence represented by SEQ IDNO: 17 or 24 or a fragment thereof and which comprise a CL comprising anamino acid sequence derived from a human CL such as the amino acidsequence represented by SEQ ID NO: 18 or 22 or a fragment thereof.

A CH comprising the amino acid sequence represented by SEQ ID NO: 17 maybe encoded by a nucleic acid comprising the nucleic acid sequencerepresented by SEQ ID NO: 20. A CH comprising the amino acid sequencerepresented by SEQ ID NO: 24 may be encoded by a nucleic acid comprisingthe nucleic acid sequence represented by SEQ ID NO: 23. A CL comprisingthe amino acid sequence represented by SEQ ID NO: 18 may be encoded by anucleic acid comprising the nucleic acid sequence represented by SEQ IDNO: 19. A CL comprising the amino acid sequence represented by SEQ IDNO: 22 may be encoded by a nucleic acid comprising the nucleic acidsequence represented by SEQ ID NO: 21.

“Fragment” or “fragment of an amino acid sequence” as used above relatesto a part of an antibody sequence, i.e. a sequence which represents theantibody sequence shortened at the N- and/or C-terminus, which when itreplaces said antibody sequence in an antibody retains binding of saidantibody to GT468 and preferably functions of said antibody as describedherein, e.g. CDC mediated lysis or ADCC mediated lysis. Preferably, afragment of an amino acid sequence comprises at least 80%, preferably atleast 90%, 95%, 96%, 97%, 98%, or 99% of the amino acid residues fromsaid amino acid sequence. Fragments of amino acid sequences describedherein may be encoded by respective fragments of nucleic acid sequencesencoding said amino acid sequences.

The present invention also relates to nucleic acids comprising genes ornucleic acid sequences encoding antibodies or parts thereof, e.g. anantibody chain, as described herein. The nucleic acids may be comprisedin a vector, e.g., a plasmid, cosmid, virus, bacteriophage or anothervector used e.g. conventionally in genetic engineering. The vector maycomprise further genes such as marker genes which allow for theselection of the vector in a suitable host cell and under suitableconditions. Furthermore, the vector may comprise expression controlelements allowing proper expression of the coding regions in suitablehosts. Such control elements are known to the artisan and may include apromoter, a splice cassette, and a translation initiation codon.

Preferably, the nucleic acid of the invention is operatively attached tothe above expression control sequences allowing expression in eukaryoticor prokaryotic cells. Control elements ensuring expression in eukaryoticor prokaryotic cells are well known to those skilled in the art.

Methods for construction of nucleic acid molecules according to thepresent invention, for construction of vectors comprising the abovenucleic acid molecules, for introduction of the vectors intoappropriately chosen host cells, for causing or achieving the expressionare well-known in the art.

A further aspect of the present invention relates to a host cellcomprising a nucleic acid or vector as disclosed herein.

Other features and advantages of the instant invention will be apparentfrom the following detailed description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. GT468 is a trophoblastic lineage marker aberrantly activated incancer cells. (A) End-point 35 cycle RT-PCR in normal tissues, primarybreast cancer samples and cancer cell lines (1, MCF-7; 2, MDA-MB-435S;3, BT-549; 4, MDA-MB-231; 5, SNU-16; 6, LCLC-103H; 7, KYSE-510; 8,KYSE-30; 9, EFO-27; 10, TOV-21G; 11, TOV-112D; 12, CAOV-3; 13, EFO-21;14, FU-OV-1; 15, LNCAP; 16, CAPAN-2). (B) Quantitative 40 cyclereal-time RT-PCR in normal tissues (1, Testis; 2, Placenta; 3, Brain; 4,Lung; 5, Breast; 6, Colon; 7, Liver; 8; Stomach; 9, Kidney; 10,Prostate; 11, Pancreas; 12, Ovary; 13, Spleen; 14, Skin; 15, Myocard;16, Endometrium; 17, rest. PBMCs; 18, prolif. PBMCs; 19, Adrenal gland),primary breast cancer specimens and (C) cancer cell lines. (D)Quantitative real-time RT-PCR analysis of siRNA-mediated GT468 silencingin MCF-7 and BT-549 breast cancer cells. (E) Western blot analysis ofsiRNA-mediated decrease of GT468 protein expression. Control cells wereeither not treated or transfected with a scrambled non-silencing duplex(ns-siRNA). (F) Western blot analysis of GT468 protein levels in normaland neoplastic human tissues. (G) Immunohistochemistry of sectionsderived from normal human breast tissue (left) and breast cancer (right)using a GT468 specific antibody.

FIG. 2. GT468 is a cell surface associated protein. (A) Staining ofmethanol-fixed and (B) non-fixed MCF-7 and BT-549 breast cancer cellswith anti-GT468/C-term antibody after transfection with GT468-specificsiRNA (siRNA#1) or non-silencing siRNA (ns-siRNA).

FIG. 3. GT468 expression promotes motility, migration and invasion ofbreast cancer cells. (A) Chemokinesis (motility) analysis in Transwellmigration assays with 5% FCS added to the upper as well as the lowerchamber was analyzed after 12 h. (B) Chemotaxis analysis of MCF-7 andBT-549 cells in Transwell migration assays 12 h after 5% FCS has beenadded to the lower chamber only to obtain a gradient. (C) Analysis ofchemotactic invasion into Matrigel 24 h after 5% FCS as chemoattractanthas been added to the lower chamber.

FIG. 4. GT468 expression promotes proliferation of breast cancer cells.(A) Analysis of proliferation in MCF-7 and BT-549 cells 72 h after knockdown has been initiated by GT468 specific siRNA duplexes. (B) Cell cycleanalysis of cells 72 h after initiation of GT468 silencing shown as barchart of cell fractions in different cell cycle states. (C) Apoptosis ofcells as determined by Annexin V staining 72 h after transfection withsiRNA. As positive control for Annexin V staining cells were treatedwith 6 μM Camptothecin for 12 h.

FIG. 5. GT468 is druggable by function-antagonizing antibodies.Proliferation analysis of MCF-7 and BT-549 cells after incubation withdifferent amounts of anti-GT468 antibody and control antibody (isotypecontrol) for 48 h.

FIG. 6. Cyclin D1 and AKT kinase are involved in GT468 function. (A)Quantitative real-time RT-PCR analysis and (B) western blot analysis ofcyclin D1 after cells were treated for 72 h with GT468 specific siRNAduplexes. Western blot analysis of AKT Ser473 phosphorylation after (C)72 h of GT468 knock down and after (D) 1 h of treatment withanti-GT468/C-term antibody.

FIG. 7. Peptide ELISA for determining the specificity of antibodiesraised against GT468 in hybridoma supernatants. Hybridoma supernatantsonly are reactive with peptides used for immunization.

FIG. 8. Staining of CHO cells transfected with a GT468-eGFP construct byhybridoma supernatants containing antibodies raised against GT468. Thehybridoma supernatants specifically stain cells expressing GT468-eGFP.

FIG. 9. GT468 is druggable by function-antagonizing monoclonalantibodies. Proliferation analysis of different cancer cell lines afterincubation with hybridoma supernatants for 72 h.

FIG. 10. Crude-lysate (CrELISA) (A) or peptide-specific ELISA (B) fordetermining the specificity of antibodies raised against GT468 inhybridoma supernatants. Hybridoma supernatants only are reactive withthe GT468 lysate (A) or the respective peptide used for immunization(B).

FIG. 11. Flowcytometric analysis for determining the specificity ofantibodies raised against GT468 in hybridoma supernatants. All hybridomasupernatants showed specific staining of GT468 transfected cells,whereas no staining was observed on mock transfected cells.

FIG. 12. Western blot for determining the specificity of antibodiesraised against GT468 in hybridoma supernatants. All hybridomasupernatants showed specific reactivity with lysates of HEK293 cellstransfected with GT468 pcDNA3.1 expression plasmid, whereas lysates ofmock transfected cells showed no signal. The faint signal of hybridomasupernatant 23-33A-1 in the mock lysate is due to spillover of the HEKGT468 lysate.

FIG. 13. Peptide ELISA to identify antibody-binding epitopes in theGT468 protein. Hybridoma supernatants 22-1A-1, 23-33A-1, and 23-19A-1each showed binding to two overlapping peptides implying reactivity to alinear epitope of GT468. The binding patterns of 22-2A-1 and 22-9B-1imply reactivity to a conformational epitope (discontinous epitope) ofthe GT468 protein.

FIG. 14. GT468 is druggable by function-antagonizing monoclonalantibodies. Proliferation analysis of different cancer cell lines afterincubation with purified hybridoma supernatants for 72 h or 120 h.

DETAILED DESCRIPTION OF THE INVENTION

The antibodies described herein may be isolated monoclonal antibodieswhich specifically bind to an epitope present on GT468, preferably anepitope located with the extracellular domain of GT468, more preferablySEQ ID NOs: 3-10 and 35-79. Isolated monoclonal antibodies encompassedby the present invention include IgA, IgG1-4, IgE, IgM, and IgDantibodies. In one embodiment the antibody is an IgG1 antibody, moreparticularly an IgG1, kappa or IgG1, lambda isotype. In anotherembodiment the antibody is an IgG3 antibody, more particularly an IgG3,kappa or IgG3, lambda isotype. In yet another embodiment the antibody isan IgG4 antibody, more particularly an IgG4, kappa or IgG4, lambdaisotype. In still another embodiment the antibody is an IgA1 or IgA2antibody. In still another embodiment the antibody is an IgM antibody.

In one embodiment the invention relates to antibodies which (i) bind tocells expressing GT468 and/or being characterized by association ofGT468 with their cell surface, and (ii) do not bind to cells notexpressing GT468 and/or not being characterized by association of GT468with their cell surface. The antibodies of the invention preferably (i)mediate killing and/or inhibit proliferation of cells expressing GT468and/or being characterized by association of GT468 with their cellsurface, and (ii) do not mediate killing and/or do not inhibitproliferation of cells not expressing GT468 and/or not beingcharacterized by association of GT468 with their cell surface.

In another embodiment, the invention relates to antibodies which (i)bind to tumor cells expressing GT468 and/or being characterized byassociation of GT468 with their cell surface, and (ii) do not bind toGT468 of non-cancer placental cells.

The invention also includes antibodies which (i) mediate killing oftumor cells expressing GT468 and/or being characterized by associationof GT468 with their cell surface, and (ii) do not mediate killing ofGT468 expressing cells of normal placenta.

Antibodies of the invention include fully human antibodies. Suchantibodies may be produced in a non-human transgenic animal, e.g., atransgenic mouse, capable of producing multiple isotypes of humanmonoclonal antibodies to GT468 by undergoing V-D-J recombination andisotype switching. Such transgenic animal can also be a transgenicrabbit for producing polyclonal antibodies such as disclosed in US2003/0017534.

Binding of an antibody of the invention to the GT468 antigen may mediatethe killing of cells expressing GT468 and/or being characterized byassociation of GT468 with their cell surface (e.g. a tumor cell), e.g.by activation of the complement system, and/or may inhibit proliferationof cells expressing GT468 and/or being characterized by association ofGT468 with their cell surface (e.g. a tumor cell). Alternatively or inaddition to mediating killing of cells expressing GT468 and/or beingcharacterized by association of GT468 with their cell surface and/orinhibiting proliferation of cells expressing GT468 and/or beingcharacterized by association of GT468 with their cell surface, bindingof an antibody of the invention to the GT468 antigen may inhibitmotility, migration and/or invasion of cells expressing GT468 and/orbeing characterized by association of GT468 with their cell surface(e.g. a tumor cell), and thus, may inhibit metastatic spread of tumorcells. The killing of cells expressing GT468 and/or being characterizedby association of GT468 with their cell surface may occur by one or moreof the following mechanisms: complement dependent cytotoxity (CDC) ofcells expressing GT468 and/or being characterized by association ofGT468 with their cell surface; apoptosis of cells expressing GT468and/or being characterized by association of GT468 with their cellsurface; effector cell phagocytosis of cells expressing GT468 and/orbeing characterized by association of GT468 with their cell surface; oreffector cell antibody dependent cellular cytotoxicity (ADCC) of cellsexpressing GT468 and/or being characterized by association of GT468 withtheir cell surface.

In order that the present invention may be more readily understood,certain terms are first defined. Additional definitions are set forththroughout the detailed description.

DEFINITION OF TERMS

The term “GT468” preferably relates to human GT468, and in particular to(i) a nucleic acid comprising a nucleic acid sequence encoding the aminosequence of SEQ ID NO: 2 such as a nucleic acid comprising the nucleicacid sequence of SEQ ID NO: 1 or (ii) a protein comprising the aminoacid sequence of SEQ ID NO: 2, and includes any variants, conformations,isoforms and species homologs thereof which are naturally expressed bycells or are expressed by cells transfected with the GT468 gene. In oneembodiment, the term “GT468” relates to the portion of GT468corresponding to the extracellular domain and preferably relates to theamino acid sequence of GT468 not including the N-terminal hydrophobicdomain. The term “GT468” includes a protein comprising amino acids 29 to119, preferably amino acids 29 to 212 and more preferably amino acids 23to 212 of SEQ ID NO: 2.

“Variants of GT468” also includes a form of GT468 consisting essentiallyof the extracellular domain or ectodomain of GT468. According to theinvention, the terms “extracellular domain” or “ectodomain” with respectto GT468 relate to the portion of GT468 which is found in associationwith the surface of cells expressing GT468. Preferably, said“extracellular domain” or “ectodomain” is present in the extracellularcompartment. The GT468 “extracellular domain” or “ectodomain” preferablyrefers to the portion of full-length GT468 which lacks the N-terminalhydrophobic domain. According to the invention, the term “hydrophobicdomain” with respect to GT468 relates to the portion of GT468 not beingpart of the extracellular domain and preferably including a hydrophobicsequence located close to the N-terminus of GT468. The “hydrophobicdomain” of GT468 may include a sequence preceding the hydrophobicsequence and being located at the N-terminal end of GT468. With respectto SEQ ID NO: 2, the N-terminal hydrophobic domain preferably comprisesamino acids 1 to 22. It will be understood that any hydrophobic domainsor sequences identified for the GT468 polypeptides of the presentinvention are identified pursuant to criteria routinely employed in theart for identifying hydrophobic domains or sequences. The exactboundaries of a hydrophobic domain may vary but most likely by no morethan about 5 amino acids at either end of the domain as initiallyidentified herein. Optionally, therefore, an extracellular domain of aGT468 polypeptide may contain from about 5 or fewer amino acids oneither side of the hydrophobic domain/extracellular domain boundary asidentified herein.

“Cell surface” is used in accordance with its normal meaning in the art,and thus includes the outside of the cell which is accessible to bindingby proteins and other molecules.

The expression “GT468 expressed on the surface of cells” means thatGT468 expressed by cells is found in association with the surface ofsaid cells.

GT468 is associated with the surface of cells if it is located at thesurface of said cells and is accessible to binding by GT468-specificantibodies added to the cells. In preferred embodiments, a cell beingcharacterized by association of GT468 with its cell surface is a cellexpressing GT468. It is to be understood that in the case where GT468 isexpressed by cells, the GT468 associated with the surface of said cellsmay only be a portion of the expressed GT468, in particular theextracellular domain thereof as defined above.

The term “GT468 variant” shall encompass (i) GT468 splice variants, (ii)GT468-posttranslationally modified variants, particularly includingvariants with different glycosylation such as N-glycosylation status,(iii) GT468 conformation variants, (iv) GT468 cancer related and GT468non-cancer related variants.

The term “raft” refers to the sphingolipid- and cholesterol-richmembrane microdomains located in the outer leaflet area of the plasmamembrane of a cell. The ability of certain proteins to associate withinsuch domains and their ability of forming “aggregates” or “focalaggregates” can effect the protein's function. For example, thetranslocation of GT468 molecules into such structures, after being boundby antibodies of the present invention, creates a high density of GT468antigen-antibody complexes in the plasma membranes. Such a high densityof GT468 antigen-antibody complexes can enable efficient activation ofthe complement system during CDC.

According to the invention, the term “disease” refers to anypathological state, including cancer, in particular those forms ofcancer described herein.

By “tumor” is meant an abnormal group of cells or tissue that grows by arapid, uncontrolled cellular proliferation and continues to grow afterthe stimuli that initiated the new growth cease. Tumors show partial orcomplete lack of structural organization and functional coordinationwith the normal tissue, and usually form a distinct mass of tissue,which may be either benign or malignant.

By “metastasis” is meant the spread of cancer cells from its originalsite to another part of the body. The formation of metastasis is a verycomplex process and depends on detachment of malignant cells from theprimary tumor, invasion of the extracellular matrix, penetration of theendothelial basement membranes to enter the body cavity and vessels, andthen, after being transported by the blood, infiltration of targetorgans. Finally, the growth of a new tumor at the target site depends onangiogenesis. Tumor metastasis often occurs even after the removal ofthe primary tumor because tumor cells or components may remain anddevelop metastatic potential. In one embodiment, the term “metastasis”according to the invention relates to “distant metastasis” which relatesto a metastasis which is remote from the primary tumor and the regionallymph node system.

The term “treatment of a disease” includes curing, shortening theduration, ameliorating, preventing, slowing down or inhibitingprogression or worsening, or preventing or delaying the onset of adisease or the symptoms thereof.

According to the invention, a sample may be any sample useful accordingto the present invention, in particular a biological sample such atissue sample, including bodily fluids, and/or a cellular sample and maybe obtained in the conventional manner such as by tissue biopsy,including punch biopsy, and by taking blood, bronchial aspirate, sputum,urine, feces or other body fluids. According to the invention, the term“biological sample” also includes fractions of biological samples.

The term “antibody” refers to a glycoprotein comprising at least twoheavy (H) chains and two light (L) chains inter-connected by disulfidebonds, or an antigen binding portion thereof. The term “antibody” alsoincludes all recombinant forms of antibodies, in particular of theantibodies described herein, e.g., antibodies expressed in prokaryotes,unglycosylated antibodies, and any antigen-binding antibody fragmentsand derivatives as described below. Each heavy chain is comprised of aheavy chain variable region (abbreviated herein as VH) and a heavy chainconstant region. Each light chain is comprised of a light chain variableregion (abbreviated herein as VL) and a light chain constant region. TheVH and VL regions can be further subdivided into regions ofhypervariability, termed complementarity determining regions (CDR),interspersed with regions that are more conserved, termed frameworkregions (FR). Each VH and VL is composed of three CDRs and four FRs,arranged from amino-terminus to carboxy-terminus in the following order:FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The variable regions of the heavyand light chains contain a binding domain that interacts with anantigen. The constant regions of the antibodies may mediate the bindingof the immunoglobulin to host tissues or factors, including variouscells of the immune system (e.g., effector cells) and the firstcomponent (C1q) of the classical complement system.

The term “humanized antibody” refers to a molecule having an antigenbinding site that is substantially derived from an immunoglobulin from anon-human species, wherein the remaining immunoglobulin structure of themolecule is based upon the structure and/or sequence of a humanimmunoglobulin. The antigen binding site may either comprise completevariable domains fused onto constant domains or only the complementaritydetermining regions (CDR) grafted onto appropriate framework regions inthe variable domains. Antigen binding sites may be wild-type or modifiedby one or more amino acid substitutions, e.g. modified to resemble humanimmunoglobulins more closely. Some forms of humanized antibodiespreserve all CDR sequences (for example a humanized mouse antibody whichcontains all six CDRs from the mouse antibody). Other forms have one ormore CDRs which are altered with respect to the original antibody.

The term “chimeric antibody” refers to those antibodies wherein oneportion of each of the amino acid sequences of heavy and light chains ishomologous to corresponding sequences in antibodies derived from aparticular species or belonging to a particular class, while theremaining segment of the chain is homologous to corresponding sequencesin another. Typically the variable region of both light and heavy chainsmimics the variable regions of antibodies derived from one species ofmammals, while the constant portions are homologous to sequences ofantibodies derived from another. One clear advantage to such chimericforms is that the variable region can conveniently be derived frompresently known sources using readily available B-cells or hybridomasfrom non-human host organisms in combination with constant regionsderived from, for example, human cell preparations. While the variableregion has the advantage of ease of preparation and the specificity isnot affected by the source, the constant region being human, is lesslikely to elicit an immune response from a human subject when theantibodies are injected than would the constant region from a non humansource. However the definition is not limited to this particularexample.

The term “antigen-binding portion” of an antibody (or simply “bindingportion”), as used herein, refers to one or more fragments of anantibody that retain the ability to specifically bind to an antigen. Ithas been shown that the antigen-binding function of an antibody can beperformed by fragments of a full-length antibody. Examples of bindingfragments encompassed within the term “antigen-binding portion” of anantibody include (i) Fab fragments, monovalent fragments consisting ofthe VL, VH, CL and CH domains; (ii) F(ab′)₂ fragments, bivalentfragments comprising two Fab fragments linked by a disulfide bridge atthe hinge region; (iii) Fd fragments consisting of the VH and CHdomains; (iv) Fv fragments consisting of the VL and VH domains of asingle arm of an antibody, (v) dAb fragments (Ward et al., (1989) Nature341: 544-546), which consist of a VH domain; (vi) isolatedcomplementarity determining regions (CDR), and (vii) combinations of twoor more isolated CDRs which may optionally be joined by a syntheticlinker. Furthermore, although the two domains of the Fv fragment, VL andVH, are coded for by separate genes, they can be joined, usingrecombinant methods, by a synthetic linker that enables them to be madeas a single protein chain in which the VL and VH regions pair to formmonovalent molecules (known as single chain Fv (scFv); see e.g., Bird etal. (1988) Science 242: 423-426; and Huston et al. (1988) Proc. Natl.Acad. Sci. USA 85: 5879-5883). Such single chain antibodies are alsointended to be encompassed within the term “antigen-binding portion” ofan antibody. A further example is binding-domain immunoglobulin fusionproteins comprising (i) a binding domain polypeptide that is fused to animmunoglobulin hinge region polypeptide, (ii) an immunoglobulin heavychain CH2 constant region fused to the hinge region, and (iii) animmunoglobulin heavy chain CH3 constant region fused to the CH2 constantregion. The binding domain polypeptide can be a heavy chain variableregion or a light chain variable region. The binding-domainimmunoglobulin fusion proteins are further disclosed in US 2003/0118592and US 2003/0133939. These antibody fragments are obtained usingconventional techniques known to those with skill in the art, and thefragments are screened for utility in the same manner as are intactantibodies.

The term “epitope” means a protein determinant capable of binding to anantibody, wherein the term “binding” herein preferably relates to aspecific binding. Epitopes usually consist of chemically active surfacegroupings of molecules such as amino acids or sugar side chains andusually have specific three dimensional structural characteristics, aswell as specific charge characteristics. Conformational andnon-conformational epitopes are distinguished in that the binding to theformer but not the latter is lost in the presence of denaturingsolvents.

The term “discontinuous epitope” as used herein, means a conformationalepitope on a protein antigen which is formed from at least two separateregions in the primary sequence of the protein.

The term “bispecific molecule” is intended to include any agent, e.g., aprotein, peptide, or protein or peptide complex, which has two differentbinding specificities. For example, the molecule may bind to, orinteract with (a) a cell surface antigen, and (b) an Fc receptor on thesurface of an effector cell. The term “multispecific molecule” or“heterospecific molecule” is intended to include any agent, e.g., aprotein, peptide, or protein or peptide complex, which has more than twodifferent binding specificities. For example, the molecule may bind to,or interact with (a) a cell surface antigen, (b) an Fc receptor on thesurface of an effector cell, and (c) at least one other component.Accordingly, the invention includes, but is not limited to, bispecific,trispecific, tetraspecific, and other multispecific molecules which aredirected to GT468, and to other targets, such as Fc receptors oneffector cells. The term “bispecific antibodies” also includesdiabodies. Diabodies are bivalent, bispecific antibodies in which the VHand VL domains are expressed on a single polypeptide chain, but using alinker that is too short to allow for pairing between the two domains onthe same chain, thereby forcing the domains to pair with complementarydomains of another chain and creating two antigen binding sites (seee.g., Holliger, P., et al. (1993) Proc. Natl. Acad. Sci. USA 90:6444-6448; Poljak, R. J., et al. (1994) Structure 2: 1121-1123).

The invention also includes derivatives of the antibodies describedherein. The term “antibody derivatives” refers to any modified form ofan antibody, e.g., a conjugate of the antibody and another agent orantibody. As used herein, an antibody is “derived from” a particulargermline sequence if the antibody is obtained from a system byimmunizing an animal or by screening an immunoglobulin gene library, andwherein the selected antibody is at least 90%, more preferably at least95%, even more preferably at least 96%, 97%, 98%, or 99% identical inamino acid sequence to the amino acid sequence encoded by the germlineimmunoglobulin gene. Typically, an antibody derived from a particulargermline sequence will display no more than 10 amino acid differences,more preferably, no more than 5, or even more preferably, no more than4, 3, 2, or 1 amino acid difference from the amino acid sequence encodedby the germline immunoglobulin gene.

As used herein, the term “heteroantibodies” refers to two or moreantibodies, derivatives thereof, or antigen binding regions linkedtogether, at least two of which have different specificities. Thesedifferent specificities include a binding specificity for an Fc receptoron an effector cell, and a binding specificity for an antigen or epitopeon a target cell, e.g., a tumor cell.

The antibodies described herein may be human antibodies. The term “humanantibody”, as used herein, is intended to include antibodies havingvariable and constant regions derived from human germline immunoglobulinsequences. The human antibodies of the invention may include amino acidresidues not encoded by human germline immunoglobulin sequences (e.g.,mutations introduced by random or site-specific mutagenesis in vitro orby somatic mutation in vivo).

The term “monoclonal antibody” as used herein refers to a preparation ofantibody molecules of single molecular composition. A monoclonalantibody displays a single binding specificity and affinity for aparticular epitope. In one embodiment, the monoclonal antibodies areproduced by a hybridoma which includes a B cell obtained from anon-human animal, e.g., mouse, fused to an immortalized cell.

The term “recombinant antibody”, as used herein, includes all antibodiesthat are prepared, expressed, created or isolated by recombinant means,such as (a) antibodies isolated from an animal (e.g., a mouse) that istransgenic or transchromosomal with respect to the immunoglobulin genesor a hybridoma prepared therefrom, (b) antibodies isolated from a hostcell transformed to express the antibody, e.g., from a transfectoma, (c)antibodies isolated from a recombinant, combinatorial antibody library,and (d) antibodies prepared, expressed, created or isolated by any othermeans that involve splicing of immunoglobulin gene sequences to otherDNA sequences.

The term “transfectoma”, as used herein, includes recombinant eukaryotichost cells expressing an antibody, such as CHO cells, NS/0 cells, HEK293cells, HEK293T cells, plant cells, or fungi, including yeast cells.

As used herein, a “heterologous antibody” is defined in relation to atransgenic organism producing such an antibody. This term refers to anantibody having an amino acid sequence or an encoding nucleic acidsequence corresponding to that found in an organism not consisting ofthe transgenic organism, and being generally derived from a speciesother than the transgenic organism.

As used herein, a “heterohybrid antibody” refers to an antibody havinglight and heavy chains of different organismal origins. For example, anantibody having a human heavy chain associated with a murine light chainis a heterohybrid antibody.

The antibodies described herein are preferably isolated. An “isolatedantibody” as used herein, is intended to refer to an antibody which issubstantially free of other antibodies having different antigenicspecificities (e.g., an isolated antibody that specifically binds toGT468 is substantially free of antibodies that specifically bindantigens other than GT468). An isolated antibody that specifically bindsto an epitope, isoform or variant of human GT468 may, however, havecross-reactivity to other related antigens, e.g., from other species(e.g., GT468 species homologs). Moreover, an isolated antibody may besubstantially free of other cellular material and/or chemicals. In oneembodiment of the invention, a combination of “isolated” monoclonalantibodies relates to antibodies having different specificities andbeing combined in a well defined composition.

According to the invention, the term “binding” preferably relates to“specific binding”. As used herein, “specific binding” refers toantibody binding to a predetermined antigen. Typically, the antibodybinds with an affinity corresponding to a KD of about 1×10⁻⁷ M or less,and binds to the predetermined antigen with an affinity corresponding toa KD that is at least two orders of magnitude lower than its affinityfor binding to a non-specific antigen (e.g., BSA, casein) other than thepredetermined antigen or a closely-related antigen.

The term “KD” (M), as used herein, is intended to refer to thedissociation equilibrium constant of a particular antibody-antigeninteraction.

As used herein, “isotype” refers to the antibody class (e.g., IgM orIgG1) that is encoded by heavy chain constant region genes.

As used herein, “isotype switching” refers to the phenomenon by whichthe class, or isotype, of an antibody changes from one Ig class to oneof the other Ig classes.

The term “naturally occurring” as used herein as applied to an objectrefers to the fact that an object can be found in nature. For example, apolypeptide or polynucleotide sequence that is present in an organism(including viruses) that can be isolated from a source in nature andwhich has not been intentionally modified by man in the laboratory isnaturally occurring.

The term “rearranged” as used herein refers to a configuration of aheavy chain or light chain immunoglobulin locus wherein a V segment ispositioned immediately adjacent to a D-J or J segment in a conformationencoding essentially a complete VH or VL domain, respectively. Arearranged immunoglobulin (antibody) gene locus can be identified bycomparison to germline DNA; a rearranged locus will have at least onerecombined heptamer/nonamer homology element.

The term “unrearranged” or “germline configuration” as used herein inreference to a V segment refers to the configuration wherein the Vsegment is not recombined so as to be immediately adjacent to a D or Jsegment.

The term “nucleic acid molecule”, as used herein, is intended to includeDNA molecules and RNA molecules. A nucleic acid molecule may besingle-stranded or double-stranded, but preferably is double-strandedDNA.

The nucleic acids described according to the invention have preferablybeen isolated. The term “isolated nucleic acid” means according to theinvention that the nucleic acid was (i) amplified in vitro, for exampleby polymerase chain reaction (PCR), (ii) recombinantly produced bycloning, (iii) purified, for example by cleavage and gel-electrophoreticfractionation, or (iv) synthesized, for example by chemical synthesis.An isolated nucleic acid is a nucleic acid which is available formanipulation by recombinant DNA techniques.

Nucleic acids may, according to the invention, be present alone or incombination with other nucleic acids, which may be homologous orheterologous. In preferred embodiments, a nucleic acid is functionallylinked to expression control sequences which may be homologous orheterologous with respect to said nucleic acid. The term “homologous”means that a nucleic acid is also functionally linked to the expressioncontrol sequence naturally and the term “heterologous” means that anucleic acid is not functionally linked to the expression controlsequence naturally.

A nucleic acid, such as a nucleic acid expressing RNA and/or protein orpeptide, and an expression control sequence are “functionally” linked toone another, if they are covalently linked to one another in such a waythat expression or transcription of said nucleic acid is under thecontrol or under the influence of said expression control sequence. Ifthe nucleic acid is to be translated into a functional protein, then,with an expression control sequence functionally linked to a codingsequence, induction of said expression control sequence results intranscription of said nucleic acid, without causing a frame shift in thecoding sequence or said coding sequence not being capable of beingtranslated into the desired protein or peptide.

The term “expression control sequence” comprises according to theinvention promoters, ribosome binding sites, enhancers and other controlelements which regulate transcription of a gene or translation of amRNA. In particular embodiments of the invention, the expression controlsequences can be regulated. The exact structure of expression controlsequences may vary as a function of the species or cell type, butgenerally comprises 5′-untranscribed and 5′- and 3′-untranslatedsequences which are involved in initiation of transcription andtranslation, respectively, such as TATA box, capping sequence, CAATsequence, and the like. More specifically, 5′-untranscribed expressioncontrol sequences comprise a promoter region which includes a promotersequence for transcriptional control of the functionally linked nucleicacid. Expression control sequences may also comprise enhancer sequencesor upstream activator sequences.

According to the invention the term “promoter” or “promoter region”relates to a nucleic acid sequence which is located upstream (5′) to thenucleic acid sequence being expressed and controls expression of thesequence by providing a recognition and binding site for RNA-polymerase.The “promoter region” may include further recognition and binding sitesfor further factors which are involved in the regulation oftranscription of a gene. A promoter may control the transcription of aprokaryotic or eukaryotic gene. Furthermore, a promoter may be“inducible” and may initiate transcription in response to an inducingagent or may be “constitutive” if transcription is not controlled by aninducing agent. A gene which is under the control of an induciblepromoter is not expressed or only expressed to a small extent if aninducing agent is absent. In the presence of the inducing agent the geneis switched on or the level of transcription is increased. This ismediated, in general, by binding of a specific transcription factor.

Promoters which are preferred according to the invention includepromoters for SP6, T3 and T7 polymerase, human U6 RNA promoter, CMVpromoter, and artificial hybrid promoters thereof (e.g. CMV) where apart or parts are fused to a part or parts of promoters of genes ofother cellular proteins such as e.g. human GAPDH(glyceraldehyde-3-phosphate dehydrogenase), and including or notincluding (an) additional intron(s).

According to the invention, the term “expression” is used in its mostgeneral meaning and comprises the production of RNA or of RNA andprotein/peptide. It also comprises partial expression of nucleic acids.Furthermore, expression may be carried out transiently or stably.

In a preferred embodiment, a nucleic acid molecule is according to theinvention present in a vector, where appropriate with a promoter, whichcontrols expression of the nucleic acid. The term “vector” is used herein its most general meaning and comprises any intermediary vehicle for anucleic acid which enables said nucleic acid, for example, to beintroduced into prokaryotic and/or eukaryotic cells and, whereappropriate, to be integrated into a genome. Vectors of this kind arepreferably replicated and/or expressed in the cells. Vectors compriseplasmids, phagemids, bacteriophages or viral genomes. The term “plasmid”as used herein generally relates to a construct of extrachromosomalgenetic material, usually a circular DNA duplex, which can replicateindependently of chromosomal DNA.

As the vector for expression of an antibody, either of a vector type inwhich the antibody heavy chain and light chain are present in differentvectors or a vector type in which the heavy chain and light chain arepresent in the same vector can be used.

The teaching given herein with respect to specific nucleic acid andamino acid sequences, e.g. those shown in the sequence listing, is to beconstrued so as to also relate to modifications of said specificsequences resulting in sequences which are functionally equivalent tosaid specific sequences, e.g. amino acid sequences exhibiting propertiesidentical or similar to those of the specific amino acid sequences andnucleic acid sequences encoding amino acid sequences exhibitingproperties identical or similar to those of the amino acid sequencesencoded by the specific nucleic acid sequences. One important propertyis to retain binding of an antibody to its target or to sustain effectorfunctions of an antibody. Preferably, a sequence modified with respectto a specific sequence, when it replaces the specific sequence in anantibody retains binding of said antibody to GT468 and preferablyfunctions of said antibody as described herein, e.g. CDC mediated lysisor ADCC mediated lysis.

It will be appreciated by those skilled in the art that in particularthe sequences of the CDR, hypervariable and variable regions can bemodified without losing the ability to bind GT468. For example, CDRregions will be either identical or highly homologous to the regions ofantibodies specified herein. By “highly homologous” it is contemplatedthat from 1 to 5, preferably from 1 to 4, such as 1 to 3 or 1 or 2substitutions may be made in the CDRs. In addition, the hypervariableand variable regions may be modified so that they show substantialhomology with the regions of antibodies specifically disclosed herein.

It is to be understood that the specific nucleic acids described hereinalso include nucleic acids modified for the sake of optimizing the codonusage in a particular host cell or organism. Differences in codon usageamong organisms can lead to a variety of problems concerningheterologous gene expression. Codon optimization by changing one or morenucleotides of the original sequence can result in an optimization ofthe expression of a nucleic acid, in particular in optimization oftranslation efficacy, in a homologous or heterologous host in which saidnucleic acid is to be expressed. For example if nucleic acids derivedfrom human and encoding constant regions and/or framework regions ofantibodies are to be used according to the present invention, e.g. forpreparing chimeric or humanised antibodies, it may be preferred tomodify said nucleic acids for the sake of optimization of codon usage,in particular if said nucleic acids, optionally fused to heterologousnucleic acids such as nucleic acids derived from other organisms asdescribed herein, are to be expressed in cells from an organismdifferent from human such as mouse or hamster. For example, the nucleicacid sequences encoding human light and heavy chain constant regionssuch as those according to SEQ ID NOs: 19 and 20, respectively, can bemodified to include one or more, preferably, at least 1, 2, 3, 4, 5, 10,15, 20 and preferably up to 10, 15, 20, 25, 30, 50, 70 or 100 or morenucleotide replacements resulting in an optimized codon usage but notresulting in a change of the amino acid sequence. Such nucleotidereplacements preferably relate to replacements of nucleotides in SEQ IDNos: 19 and 20, respectively, selected from the replacements shown inthe following alignment of SEQ ID Nos: 19 and 20, respectively, withtheir modified counterparts and not resulting in a change in the encodedamino acid sequence or relate to corresponding replacements atcorresponding positions in other nucleic acid sequences encoding humanlight and heavy chain constant regions, respectively. Preferably, all ofthe replacements shown in the following alignments of SEQ ID Nos: 19 and20, respectively, with their modified counterparts not resulting in achange in the encoded amino acid sequence are effected in nucleic acidsequences encoding human light and heavy chain constant regions,respectively.

Furthermore, it may be desired according to the present invention tomodify the amino acid sequences described herein, in particular those ofhuman heavy chain constant regions to adapt the sequence to a desiredallotype, e.g. an allotype found in the Caucasian population. Suchmodifications are preferably selected from the group consisting of thefollowing amino acid replacements within SEQ ID NO: 17 or atcorresponding positions within other human heavy chain constant regions:K93R, D235E, and L237M. Preferably, all of these modifications areincluded in amino acid sequences of human heavy chain constant regions.

According the invention, the term “corresponding positions” relates tonucleotides or amino acid residues which in a sequence alignment of twonucleic acid or protein sequences are aligned to each other.

Preferably the degree of identity between a specific nucleic acidsequence described herein and a nucleic acid sequence which is modifiedwith respect to or which is a variant of said specific nucleic acidsequence will be at least 70%, preferably at least 75%, more preferablyat least 80%, even more preferably at least 90% or most preferably atleast 95%, 96%, 97%, 98% or 99%. Regarding GT468 nucleic acid variants,the degree of identity is preferably given for a region of at leastabout 300, at least about 400, at least about 450, at least about 500,at least about 550, at least about 600 or at least about 630nucleotides. In preferred embodiments, the degree of identity is givenfor the entire length of the reference nucleic acid sequence, such asthe nucleic acid sequences given in the sequence listing. Preferably,the two sequences are capable of hybridizing and forming a stable duplexwith one another, with hybridization preferably being carried out underconditions which allow specific hybridization between polynucleotides(stringent conditions). Stringent conditions are described, for example,in Molecular Cloning: A Laboratory Manual, J. Sambrook et al., Editors,2nd Edition, Cold Spring Harbor Laboratory press, Cold Spring Harbor,N.Y., 1989 or Current Protocols in Molecular Biology, F. M. Ausubel etal., Editors, John Wiley & Sons, Inc., New York and refer, for example,to hybridization at 65° C. in hybridization buffer (3.5×SSC, 0.02%Ficoll, 0.02% polyvinylpyrrolidone, 0.02% bovine serum albumin, 2.5 mMNaH₂PO₄ (pH 7), 0.5% SDS, 2 mM EDTA). SSC is 0.15 M sodium chloride/0.15M sodium citrate, pH 7. After hybridization, the membrane to which theDNA has been transferred is washed, for example, in 2×SSC at roomtemperature and then in 0.1-0.5×SSC/0.1×SDS at temperatures of up to 68°C.

Preferably the degree of similarity, preferably identity between aspecific amino acid sequence described herein and an amino acid sequencewhich is modified with respect to or which is a variant of said specificamino acid sequence such as between amino acid sequences showingsubstantial homology will be at least 70%, preferably at least 80%, evenmore preferably at least 90% or most preferably at least 95%, 96%, 97%,98% or 99%. Regarding GT468 polypeptide variants, the degree ofsimilarity or identity is given preferably for a region of at leastabout 100, at least about 120, at least about 140, at least about 160,at least about 180, at least about 200, at least about 210 or 212 aminoacids. In preferred embodiments, the degree of similarity or identity isgiven for the entire length of the reference amino acid sequence such asthe amino acid sequences given in the sequence listing.

All of the above described modified sequences or sequence variants arewithin the scope of the present invention.

“Sequence similarity” indicates the percentage of amino acids thateither are identical or that represent conservative amino acidsubstitutions. “Sequence identity” between two polypeptide or nucleicacid sequences indicates the percentage of amino acids or nucleotidesthat are identical between the sequences.

The “percentage identity” is obtained after the best alignment, thispercentage being purely statistical and the differences between the twosequences being distributed randomly and over their entire length.Sequence comparisons between two nucleotide or amino acid sequences areconventionally carried out by comparing these sequences after havingaligned them optimally, said comparison being carried out by segment orby “window of comparison” in order to identify and compare local regionsof sequence similarity. The optimal alignment of the sequences forcomparison may be produced, besides manually, by means of the localhomology algorithm of Smith and Waterman, 1981, Ads App. Math. 2, 482,by means of the local homology algorithm of Neddleman and Wunsch, 1970,J. Mol. Biol. 48, 443, by means of the similarity search method ofPearson and Lipman, 1988, Proc. Natl. Acad. Sci. USA 85, 2444, or bymeans of computer programs which use these algorithms (GAP, BESTFIT,FASTA, BLAST P, BLAST N and TFASTA in Wisconsin Genetics SoftwarePackage, Genetics Computer Group, 575 Science Drive, Madison, Wis.).

The percentage identity is calculated by determining the number ofidentical positions between the two sequences being compared, dividingthis number by the number of positions compared and multiplying theresult obtained by 100 so as to obtain the percentage identity betweenthese two sequences.

“Conservative substitutions,” may be made, for instance, on the basis ofsimilarity in polarity, charge, solubility, hydrophobicity,hydrophilicity, and/or the amphipathic nature of the residues involved.For example: (a) nonpolar (hydrophobic) amino acids include alanine,leucine, isoleucine, valine, proline, phenylalanine, tryptophan, andmethionine; (b) polar neutral amino acids include glycine, serine,threonine, cysteine, tyrosine, asparagine, and glutamine; (c) positivelycharged (basic) amino acids include arginine, lysine, and histidine; and(d) negatively charged (acidic) amino acids include aspartic acid andglutamic acid. Substitutions typically may be made within groups(a)-(d). In addition, glycine and proline may be substituted for oneanother based on their ability to disrupt α-helices. Some preferredsubstitutions may be made among the following groups: (i) S and T; (ii)P and G; and (iii) A, V, L and I. Given the known genetic code, andrecombinant and synthetic DNA techniques, the skilled scientist readilycan construct DNAs encoding the conservative amino acid variants.

The present invention comprises antibodies in which alterations havebeen made in the Fc region in order to change the functional orpharmacokinetic properties of the antibodies. Such alterations mayresult in a decrease or increase of C1q binding and CDC or of FcγRbinding and ADCC. Substitutions can, for example, be made in one or moreof the amino acid residues of the heavy chain constant region, therebycausing an alteration in an effector function while retaining theability to bind to the antigen as compared with the modified antibody,cf. U.S. Pat. No. 5,624,821 and U.S. Pat. No. 5,648,260.

The in vivo half-life of antibodies can be improved by modifying thesalvage receptor epitope of the Ig constant domain or an Ig-likeconstant domain such that the molecule does not comprise an intact CH2domain or an intact Ig Fc region, cf. U.S. Pat. No. 6,121,022 and U.S.Pat. No. 6,194,551. The in vivo half-life can furthermore be increasedby making mutations in the Fc region, e.g., by substituting threoninefor leucine at position 252, by substituting threonine for serine atposition 254, or by substituting threonine for phenylalanine at position256, cf. U.S. Pat. No. 6,277,375.

Furthermore, the glycosylation pattern of antibodies can be modified inorder to change the effector function of the antibodies. For example,the antibodies can be expressed in a transfectoma which does not add thefucose unit normally attached to Asn at position 297 of the Fc region inorder to enhance the affinity of the Fc region for Fc-Receptors which,in turn, will result in an increased ADCC of the antibodies in thepresence of NK cells, cf. Shield et al. (2002) JBC, 277: 26733.Furthermore, modification of galactosylation can be made in order tomodify CDC.

Alternatively, in another embodiment, mutations can be introducedrandomly along all or part of a anti-GT468 antibody coding sequence,such as by saturation mutagenesis, and the resulting modified anti-GT468antibodies can be screened for binding activity.

The term “recombinant host cell” (or simply “host cell”), as usedherein, is intended to refer to a cell into which a recombinantexpression vector has been introduced. It should be understood that suchterms are intended to refer not only to the particular subject cell butto the progeny of such a cell. Because certain modifications may occurin succeeding generations due to either mutation or environmentalinfluences, such progeny may not, in fact, be identical to the parentcell, but are still included within the scope of the term “host cell” asused herein. Recombinant host cells include, for example, transfectomas,such as CHO cells, NS/0 cells, and lymphocytic cells.

As used herein, the term “subject” includes any human or non-humananimal. The term “non-human animal” includes all vertebrates, e.g.,mammals and non-mammals, such as non-human primates, sheep, dog, cow,chickens, amphibians, reptiles, etc.

The terms “transgenic animal” refers to an animal having a genomecomprising one or more transgenes, preferably heavy and/or light chaintransgenes, or transchromosomes (either integrated or non-integratedinto the animal's natural genomic DNA) and which is preferably capableof expressing the transgenes. For example, a transgenic mouse can have ahuman light chain transgene and either a human heavy chain transgene orhuman heavy chain transchromosome, such that the mouse produces humananti-GT468 antibodies when immunized with GT468 antigen and/or cellsexpressing GT468. The human heavy chain transgene can be integrated intothe chromosomal DNA of the mouse, as is the case for transgenic mice,e.g., HuMAb mice, such as HCo7 or HCo12 mice, or the human heavy chaintransgene can be maintained extrachromosomally, as is the case fortranschromosomal (e.g., KM) mice as described in WO 02/43478. Suchtransgenic and transchromosomal mice may be capable of producingmultiple isotypes of human monoclonal antibodies to GT468 (e.g., IgG,IgA and/or IgE) by undergoing V-D-J recombination and isotype switching.

“Reduce” or “inhibit” as used herein means the ability to cause anoverall decrease, preferably of 5% or greater, 10% or greater, 20% orgreater, more preferably of 50% or greater, and most preferably of 75%or greater, in the level, e.g. in the level of proliferation of cells.

Mechanisms of mAb Action

Although the following provides considerations regarding the mechanismunderlying the therapeutic efficacy of antibodies of the invention it isnot to be considered as limiting to the invention in any way.

The antibodies described herein preferably interact with components ofthe immune system, preferably through ADCC or CDC. Antibodies of theinvention can also be used to target payloads (e.g., radioisotopes,drugs or toxins) to directly kill tumor cells or can be usedsynergistically with traditional chemotherapeutic agents, attackingtumors through complementary mechanisms of action that may includeanti-tumor immune responses that may have been compromised owing to achemotherapeutic's cytotoxic side effects on T lymphocytes. However,antibodies of the invention may also exert an effect simply by bindingto GT468 on the cell surface, thus, e.g. blocking proliferation of thecells.

Antibody-Dependent Cell-Mediated Cytotoxicity

ADCC describes the cell-killing ability of effector cells as describedherein, in particular lymphocytes, which preferably requires the targetcell being marked by an antibody.

ADCC preferably occurs when antibodies bind to antigens on tumor cellsand the antibody Fc domains engage Fc receptors (FcR) on the surface ofimmune effector cells. Several families of Fc receptors have beenidentified, and specific cell populations characteristically expressdefined Fc receptors. ADCC can be viewed as a mechanism to directlyinduce a variable degree of immediate tumor destruction that leads toantigen presentation and the induction of tumor-directed T-cellresponses. Preferably, in vivo induction of ADCC will lead to tumordirected T-cell responses and host-derived antibody responses.

Complement-Dependent Cytotoxicity

CDC is another cell-killing method that can be directed by antibodies.IgM is the most effective isotype for complement activation. IgG1 andIgG3 are also both very effective at directing CDC via the classicalcomplement-activation pathway. Preferably, in this cascade, theformation of antigen-antibody complexes results in the uncloaking ofmultiple C 1 q binding sites in close proximity on the C_(H)2 domains ofparticipating antibody molecules such as IgG molecules (C1q is one ofthree subcomponents of complement C1). Preferably these uncloaked C1qbinding sites convert the previously low-affinity C1q-IgG interaction toone of high avidity, which triggers a cascade of events involving aseries of other complement proteins and leads to the proteolytic releaseof the effector-cell chemotactic/activating agents C3a and C5a.Preferably, the complement cascade ends in the formation of a membraneattack complex, which creates pores in the cell membrane that facilitatefree passage of water and solutes into and out of the cell.

Production of Antibodies

Antibodies of the invention can be produced by a variety of techniques,including conventional monoclonal antibody methodology, e.g., thestandard somatic cell hybridization technique of Kohler and Milstein,Nature 256: 495 (1975). Although somatic cell hybridization proceduresare preferred, in principle, other techniques for producing monoclonalantibodies can be employed, e.g., viral or oncogenic transformation ofB-lymphocytes or phage display techniques using libraries of antibodygenes.

The preferred animal system for preparing hybridomas that secretemonoclonal antibodies is the murine system. Hybridoma production in themouse is a very well established procedure. Immunization protocols andtechniques for isolation of immunized splenocytes for fusion are knownin the art. Fusion partners (e.g., murine myeloma cells) and fusionprocedures are also known.

Other preferred animal systems for preparing hybridomas that secretemonoclonal antibodies are the rat and the rabbit system (e.g. describedin Spieker-Polet et al., Proc. Natl. Acad. Sci. U.S.A. 92:9348 (1995),see also Rossi et al., Am. J. Clin. Pathol. 124: 295 (2005)).

In yet another preferred embodiment, human monoclonal antibodiesdirected against GT468 can be generated using transgenic ortranschromosomal mice carrying parts of the human immune system ratherthan the mouse system. These transgenic and transchromosomic miceinclude mice known as HuMAb mice and KM mice, respectively, and arecollectively referred to herein as “transgenic mice.” The production ofhuman antibodies in such transgenic mice can be performed as describedin detail for CD20 in WO2004 035607.

Yet another strategy for generating monoclonal antibodies is to directlyisolate genes encoding antibodies from lymphocytes producing antibodiesof defined strategy e.g. see Babcock et al., 1996; A novel strategy forgenerating monoclonal antibodies from single, isolated lymphocytesproducing antibodies of defined strategy. For details of recombinantantibody engineering see also Welschof and Kraus, Recombinant antibodiesfor cancer therapy ISBN-0-89603-918-8 and Benny K. C. Lo AntibodyEngineering ISBN 1-58829-092-1.

Immunizations

To generate antibodies to GT468, mice can be immunized withcarrier-conjugated peptides derived from the GT468 sequence, an enrichedpreparation of recombinantly expressed GT468 antigen or fragmentsthereof and/or cells expressing GT468, as described. Alternatively, micecan be immunized with DNA encoding full length human GT468 (e.g. SEQ IDNO: 1) or fragments thereof, in particular those encoding SEQ IDNos:3-10 and 35-79. In the event that immunizations using a purified orenriched preparation of the GT468 antigen do not result in antibodies,mice can also be immunized with cells expressing GT468, e.g., a cellline, to promote immune responses.

The immune response can be monitored over the course of the immunizationprotocol with plasma and serum samples being obtained by tail vein orretroorbital bleeds. Mice with sufficient titers of anti-GT468immunoglobulin can be used for fusions. Mice can be boostedintraperitonealy or intravenously with GT468 expressing cells 3 daysbefore sacrifice and removal of the spleen to increase the rate ofspecific antibody secreting hybridomas.

Generation of Hybridomas Producing Monoclonal Antibodies

To generate hybridomas producing monoclonal antibodies to GT468,splenocytes and lymph node cells from immunized mice can be isolated andfused to an appropriate immortalized cell line, such as a mouse myelomacell line. The resulting hybridomas can then be screened for theproduction of antigen-specific antibodies. Individual wells can then bescreened by ELISA for antibody secreting hybridomas. ByImmunofluorescence and FACS analysis using GT468 expressing cells,antibodies with specificity for GT468 can be identified. The antibodysecreting hybridomas can be replated, screened again, and if stillpositive for anti-GT468 monoclonal antibodies can be subcloned bylimiting dilution. The stable subclones can then be cultured in vitro togenerate antibody in tissue culture medium for characterization.

Generation of Transfectomas Producing Monoclonal Antibodies

Antibodies of the invention also can be produced in a host celltransfectoma using, for example, a combination of recombinant DNAtechniques and gene transfection methods as are well known in the art(Morrison, S. (1985) Science 229: 1202).

For example, in one embodiment, the gene(s) of interest, e.g., antibodygenes, can be ligated into an expression vector such as a eukaryoticexpression plasmid such as used by the GS gene expression systemdisclosed in WO 87/04462, WO 89/01036 and EP 338 841 or other expressionsystems well known in the art. The purified plasmid with the clonedantibody genes can be introduced in eukaryotic host cells such as CHOcells, NS/0 cells, HEK293T cells or HEK293 cells or alternatively othereukaryotic cells like plant derived cells, fungal or yeast cells. Themethod used to introduce these genes can be methods described in the artsuch as electroporation, lipofectine, lipofectamine or others. Afterintroduction of these antibody genes in the host cells, cells expressingthe antibody can be identified and selected. These cells represent thetransfectomas which can then be amplified for their expression level andupscaled to produce antibodies. Recombinant antibodies can be isolatedand purified from these culture supernatants and/or cells.

Alternatively, the cloned antibody genes can be expressed in otherexpression systems, including prokaryotic cells, such as microorganisms,e.g. E. coli. Furthermore, the antibodies can be produced in transgenicnon-human animals, such as in milk from sheep and rabbits or in eggsfrom hens, or in transgenic plants; see e.g. Verma, R., et al. (1998) J.Immunol. Meth. 216: 165-181; Pollock, et al. (1999) J. Immunol. Meth.231: 147-157; and Fischer, R., et al. (1999) Biol. Chem. 380: 825-839.

Use of Partial Antibody Sequences to Express Intact Antibodies (i.e.Humanization and Chimerisation).

a) Chimerization

Murine monoclonal antibodies can be used as therapeutic antibodies inhumans when labeled with toxins or radioactive isotopes. Nonlabeledmurine antibodies are highly immunogenic in man when repetitivelyapplied leading to reduction of the therapeutic effect. The mainimmunogenicity is mediated by the heavy chain constant regions. Theimmunogenicity of murine antibodies in man can be reduced or completelyavoided if respective antibodies are chimerized or humanized. Chimericantibodies are antibodies, the different portions of which are derivedfrom different animal species, such as those having a variable regionderived from a murine antibody and a human immunoglobulin constantregion. Chimerisation of antibodies is achieved by joining of thevariable regions of the murine antibody heavy and light chain with theconstant region of human heavy and light chain (e.g. as described byKraus et al., in Methods in Molecular Biology series, Recombinantantibodies for cancer therapy ISBN-0

89603-918-8). In a preferred embodiment chimeric antibodies aregenerated by joining human kappa-light chain constant region to murinelight chain variable region. In an also preferred embodiment chimericantibodies can be generated by joining human lambda-light chain constantregion to murine light chain variable region. The preferred heavy chainconstant regions for generation of chimeric antibodies are IgG1, IgG3and IgG4. Other preferred heavy chain constant regions for generation ofchimeric antibodies are IgG2, IgA, IgD and IgM.

b) Humanization

Antibodies interact with target antigens predominantly through aminoacid residues that are located in the six heavy and light chaincomplementarity determining regions (CDRs). For this reason, the aminoacid sequences within CDRs are more diverse between individualantibodies than sequences outside of CDRs. Because CDR sequences areresponsible for most antibody-antigen interactions, it is possible toexpress recombinant antibodies that mimic the properties of specificnaturally occurring antibodies by constructing expression vectors thatinclude CDR sequences from the specific naturally occurring antibodygrafted onto framework sequences from a different antibody withdifferent properties (see, e.g., Riechmann, L. et al. (1998) Nature 332:323-327; Jones, P. et al. (1986) Nature 321: 522-525; and Queen, C. etal. (1989) Proc. Natl. Acad. Sci. U.S.A. 86: 10029-10033). Suchframework sequences can be obtained from public DNA databases thatinclude germline antibody gene sequences. These germline sequences willdiffer from mature antibody gene sequences because they will not includecompletely assembled variable genes, which are formed by V (D) J joiningduring B cell maturation. Germline gene sequences will also differ fromthe sequences of a high affinity secondary repertoire antibody atindividual evenly across the variable region. For example, somaticmutations are relatively infrequent in the amino terminal portion offramework region 1 and in the carboxy-terminal portion of frameworkregion 4. Furthermore, many somatic mutations do not significantly alterthe binding properties of the antibody. For this reason, it is notnecessary to obtain the entire DNA sequence of a particular antibody inorder to recreate an intact recombinant antibody having bindingproperties similar to those of the original antibody (see WO 99/45962).Partial heavy and light chain sequences spanning the CDR regions aretypically sufficient for this purpose. The partial sequence is used todetermine which germline variable and joining gene segments contributedto the recombined antibody variable genes. The germline sequence is thenused to fill in missing portions of the variable regions. Heavy andlight chain leader sequences are cleaved during protein maturation anddo not contribute to the properties of the final antibody. To addmissing sequences, cloned cDNA sequences can be combined with syntheticoligonucleotides by ligation or PCR amplification. Alternatively, theentire variable region can be synthesized as a set of short,overlapping, oligonucleotides and combined by PCR amplification tocreate an entirely synthetic variable region clone. This process hascertain advantages such as elimination or inclusion or particularrestriction sites, or optimization of particular codons.

The nucleotide sequences of heavy and light chain transcripts fromhybridomas are used to design an overlapping set of syntheticoligonucleotides to create synthetic V sequences with identical aminoacid coding capacities as the natural sequences. The synthetic heavy andkappa chain sequences can differ from the natural sequences in threeways: strings of repeated nucleotide bases are interrupted to facilitateoligonucleotide synthesis and PCR amplification; optimal translationinitiation sites are incorporated according to Kozak's rules (Kozak,1991, J. Biol. Chem. 266: 19867-19870); and HindIII sites are engineeredupstream of the translation initiation sites.

For both the heavy and light chain variable regions, the optimizedcoding and corresponding non-coding, strand sequences are broken downinto 30-50 nucleotides approximately at the midpoint of thecorresponding non-coding oligonucleotide. Thus, for each chain, theoligonucleotides can be assembled into overlapping double stranded setsthat span segments of 150-400 nucleotides. The pools are then used astemplates to produce PCR amplification products of 150-400 nucleotides.Typically, a single variable region oligonucleotide set will be brokendown into two pools which are separately amplified to generate twooverlapping PCR products. These overlapping products are then combinedby PCR amplification to form the complete variable region. It may alsobe desirable to include an overlapping fragment of the heavy or lightchain constant region in the PCR amplification to generate fragmentsthat can easily be cloned into the expression vector constructs.

The reconstructed chimerized or humanized heavy and light chain variableregions are then combined with cloned promoter, leader, translationinitiation, constant region, 3′ untranslated, polyadenylation, andtranscription termination sequences to form expression vectorconstructs. The heavy and light chain expression constructs can becombined into a single vector, co-transfected, serially transfected, orseparately transfected into host cells which are then fused to form ahost cell expressing both chains. Plasmids for use in construction ofexpression vectors for human IgGκ are described below. The plasmids wereconstructed so that PCR amplified V heavy and V kappa light chain cDNAsequences could be used to reconstruct complete heavy and light chainminigenes. These plasmids can be used to express completely human, orchimeric IgG1, Kappa or IgG4, Kappa antibodies. Similar plasmids can beconstructed for expression of other heavy chain isotypes, or forexpression of antibodies comprising lambda light chains.

Thus, in another aspect of the invention, the structural features of theanti-GT468 antibodies of the invention, are used to create structurallyrelated humanized anti-GT468 antibodies that retain at least onefunctional property of the antibodies of the invention, such as bindingto GT468. More specifically, one or more CDR regions of mouse monoclonalantibodies can be combined recombinantly with known human frameworkregions and CDRs to create additional, recombinantly-engineered,humanized anti-GT468 antibodies of the invention.

Binding to Antigen Expressing Cells

The ability of the antibody to bind GT468 can be determined usingstandard binding assays, such as those set forth in the examples (e.g.,ELISA, Western Blot, Immunofluorescence and flow cytometric analysis).

Characterization of Binding of Antibodies

To purify anti-GT468 antibodies, selected hybridomas can be grown intwo-liter spinner-flasks for monoclonal antibody purification.Alternatively, anti-GT468 antibodies can be produced in dialysis basedbioreactors. Supernatants can be filtered and, if necessary,concentrated before affinity chromatography with protein G-sepharose orprotein A-sepharose. Eluted IgG can be checked by gel electrophoresisand high performance liquid chromatography to ensure purity. The buffersolution can be exchanged into PBS, and the concentration can bedetermined by OD280 using 1.43 extinction coefficient. The monoclonalantibodies can be aliquoted and stored at −80° C.

To determine if the selected anti-GT468 monoclonal antibodies bind tounique epitopes, site-directed or multi-site directed mutagenesis can beused.

Isotype Determination

To determine the isotype of purified antibodies, isotype ELISAs withvarious commercial kits (e.g. Zymed, Roche Diagnostics) can beperformed. Wells of microtiter plates can be coated with anti-mouse Ig.After blocking, the plates are reacted with monoclonal antibodies orpurified isotype controls, at ambient temperature for two hours. Thewells can then be reacted with either mouse IgG1, IgG2a, IgG2b or IgG3,IgA or mouse IgM-specific peroxidase-conjugated probes. After washing,the plates can be developed with ABTS substrate (1 mg/ml) and analyzedat OD of 405-650. Alternatively, the IsoStrip Mouse Monoclonal AntibodyIsotyping Kit (Roche, Cat. No. 1493027) may be used as described by themanufacturer.

Flow Cytometric Analysis

In order to demonstrate presence of anti-GT468 antibodies in sera ofimmunized mice or binding of monoclonal antibodies to living cellsexpressing GT468, flow cytometry can be used. Cell lines expressingnaturally or after transfection GT468 and negative controls lackingGT468 expression (grown under standard growth conditions) can be mixedwith various concentrations of monoclonal antibodies in hybridomasupernatants or in PBS containing 1% FBS, and can be incubated at 4° C.for 30 min. After washing, the APC- or Alexa647-labeled anti IgGantibody can bind to GT468-bound monoclonal antibody under the sameconditions as the primary antibody staining. The samples can be analyzedby flow cytometry with a FACS instrument using light and side scatterproperties to gate on single, living cells. In order to distinguishGT468-specific monoclonal antibodies from non-specific binders in asingle measurement, the method of co-transfection can be employed. Cellstransiently transfected with plasmids encoding GT468 and a fluorescentmarker can be stained as described above. Transfected cells can bedetected in a different fluorescence channel than antibody-stainedcells. As the majority of transfected cells express both transgenes,GT468-specific monoclonal antibodies bind preferentially to fluorescencemarker expressing cells, whereas non-specific antibodies bind in acomparable ratio to non-transfected cells. An alternative assay usingfluorescence microscopy may be used in addition to or instead of theflow cytometry assay. Cells can be stained exactly as described aboveand examined by fluorescence microscopy.

Immunofluorescence Microscopy

In order to demonstrate presence of anti-GT468 antibodies in sera ofimmunized mice or binding of monoclonal antibodies to living cellsexpressing GT468, immunofluorescence microscopy analysis can be used.For example, cell lines expressing either spontaneously or aftertransfection GT468 and negative controls lacking GT468 expression aregrown in chamber slides under standard growth conditions in DMEM/F12medium, supplemented with 10% fetal calf serum (FCS), 2 mM L-glutamine,100 IU/ml penicillin and 100 μg/ml streptomycin. Cells can then be fixedwith methanol or paraformaldehyde or left untreated. Cells can then bereacted with monoclonal antibodies against GT468 for 30 min. at 25° C.After washing, cells can be reacted with an Alexa555-labelled anti-mouseIgG secondary antibody (Molecular Probes) under the same conditions.Cells can then be examined by fluorescence microscopy.

Total GT468 levels in cells can be observed when cells are methanolfixed or paraformaldehyde fixed and permeabilized with Triton X-100. Inliving cells and non-permeabilized, paraformaldehyde fixed cells surfacelocalization of GT468 can be examined. Additionally targeting of GT468to tight junctions can be analyzed by co-staining with tight junctionmarkers such as ZO-1. Furthermore, effects of antibody binding and GT468localization within the cell membrane can be examined.

Western Blot

Anti-GT468 IgG can be further tested for reactivity with GT468 antigenby Western Blotting. Briefly, cell extracts from cells expressing GT468and appropriate negative controls can be prepared and subjected tosodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. Afterelectrophoresis, the separated antigens will be transferred tonitrocellulose membranes, blocked, and probed with the monoclonalantibodies to be tested. IgG binding can be detected using anti-mouseIgG peroxidase and developed with ECL substrate.

Immunohistochemistry

Anti-GT468 mouse IgGs can be further tested for reactivity with GT468antigen by Immunohistochemistry in a manner well known to the skilledperson, e.g. using paraformaldehyde or acetone fixed cyrosections orparaffin embedded tissue sections fixed with paraformaldehyde fromnon-cancer tissue or cancer tissue samples obtained from patients duringroutine surgical procedures or from mice carrying xenografted tumorsinoculated with cell lines expressing spontaneously or aftertransfection GT468. For immunostaining, antibodies reactive to GT468 canbe incubated followed by horseradish-peroxidase conjugated goatanti-mouse or goat anti-rabbit antibodies (DAKO) according to thevendors instructions.

Phagocytic and Cell Killing Activities of Antibodies In Vitro

In addition to binding specifically to GT468, anti-GT468 antibodies canbe tested for their ability to mediate phagocytosis and killing of cellsexpressing GT468 and/or being characterized by association of GT468 withtheir cell surface. The testing of monoclonal antibody activity in vitrowill provide an initial screening prior to testing in vivo models.

Antibody Dependent Cell-Mediated Cytotoxicity (ADCC):

Briefly, polymorphonuclear cells (PMNs), NK cells, monocytes,mononuclear cells or other effector cells, from healthy donors can bepurified by Ficoll Hypaque density centrifugation, followed by lysis ofcontaminating erythrocytes. Washed effector cells can be suspended inRPMI supplemented with 10% heat-inactivated fetal calf serum or,alternatively with 5% heat-inactivated human serum and mixed with ⁵¹Crlabeled target cells expressing GT468 and/or being characterized byassociation of GT468 with their cell surface, at various ratios ofeffector cells to target cells. Alternatively, the target cells may belabeled with a fluorescence enhancing ligand (BATDA). A highlyfluorescent chelate of Europium with the enhancing ligand which isreleased from dead cells can be measured by a fluorometer. Anotheralternative technique may utilize the transfection of target cells withluciferase. Added lucifer yellow may then be oxidated by viable cellsonly. Purified anti-GT468 IgGs can then be added at variousconcentrations. Irrelevant human IgG can be used as negative control.Assays can be carried out for 4 to 20 hours at 37° C. depending on theeffector cell type used. Samples can be assayed for cytolysis bymeasuring ⁵¹Cr release or the presence of the EuTDA chelate in theculture supernatant. Alternatively, luminescence resulting from theoxidation of lucifer yellow can be a measure of viable cells.

Anti-GT468 monoclonal antibodies can also be tested in variouscombinations to determine whether cytolysis is enhanced with multiplemonoclonal antibodies.

Complement Dependent Cytotoxicity (CDC):

Monoclonal anti-GT468 antibodies can be tested for their ability tomediate CDC using a variety of known techniques. For example, serum forcomplement can be obtained from blood in a manner known to the skilledperson. To determine the CDC activity of mAbs, different methods can beused. ⁵¹Cr release can for example be measured or elevated membranepermeability can be assessed using a propidium iodide (PI) exclusionassay. Briefly, target cells can be washed and 5×10⁵/ml can be incubatedwith various concentrations of mAb for 10-30 min. at room temperature orat 37° C. Serum or plasma can then be added to a final concentration of20% (v/v) and the cells incubated at 37° C. for 20-30 min. All cellsfrom each sample can be added to the PI solution in a FACS tube. Themixture can then be analyzed immediately by flow cytometry analysisusing FACSArray.

In an alternative assay, induction of CDC can be determined on adherentcells. In one embodiment of this assay, cells are seeded 24 h before theassay with a density of 3×10⁴/well in tissue-culture flat-bottommicrotiter plates. The next day growth medium is removed and the cellsare incubated in triplicates with antibodies. Control cells areincubated with growth medium or growth medium containing 0.2% saponinfor the determination of background lysis and maximal lysis,respectively. After incubation for 20 min. at room temperaturesupernatant is removed and 20% (v/v) human plasma or serum in DMEM(prewarmed to 37° C.) is added to the cells and incubated for another 20min. at 37° C. All cells from each sample are added to propidium iodidesolution (10 μg/ml). Then, supernatants are replaced by PBS containing2.5 μg/ml ethidium bromide and fluorescence emission upon excitation at520 nm is measured at 600 nm using a Tecan Safire. The percentagespecific lysis is calculated as follows: % specific lysis=(fluorescencesample-fluorescence background)/(fluorescence maximal lysis-fluorescencebackground)×100.

Inhibition of Cell Proliferation by Monoclonal Antibodies:

To test for the ability to initiate apoptosis, monoclonal anti-GT468antibodies can, for example, be incubated with GT468 positive tumorcells or GT468 transfected tumor cells at 37° C. for about 20 hours. Thecells can be harvested, washed in Annexin-V binding buffer (BDbiosciences), and incubated with Annexin V conjugated with FITC or APC(BD biosciences) for 15 min. in the dark. All cells from each sample canbe added to PI solution (10 μg/ml in PBS) in a FACS tube and assessedimmediately by flow cytometry (as above).

Alternatively, a general inhibition of cell-proliferation by monoclonalantibodies can be detected with commercially available kits. The DELFIACell Proliferation Kit (Perkin-Elmer, Cat. No. AD0200) is a non-isotopicimmunoassay based on the measurement of 5-bromo-2′-deoxyuridine (BrdU)incorporation during DNA synthesis of proliferating cells inmicroplates. Incorporated BrdU is detected using europium labelledmonoclonal antibody. To allow antibody detection, cells are fixed andDNA denatured using Fix solution. Unbound antibody is washed away andDELFIA inducer is added to dissociate europium ions from the labelledantibody into solution, where they form highly fluorescent chelates withcomponents of the DELFIA Inducer. The fluorescence measured—utilizingtime-resolved fluorometry in the detection—is proportional to the DNAsynthesis in the cell of each well.

Preclinical Studies

Monoclonal antibodies which bind to GT468 also can be tested in an invivo model (e.g. in immune deficient mice carrying xenografted tumorsinoculated with cell lines expressing GT468, possibly aftertransfection) to determine their efficacy in controlling growth ofGT468-expressing tumor cells.

In vivo studies after xenografting GT468 expressing tumor cells intoimmunocompromised mice or other animals can be performed usingantibodies of the invention. Antibodies can be adminstered to tumor freemice followed by injection of tumor cells to measure the effects of theantibodies to prevent formation of tumors or tumor-related symptoms.Antibodies can be adminstered to tumor-bearing mice to determine thetherapeutic efficacy of respective antibodies to reduce tumor growth,metastasis or tumor related symptoms. Antibody application can becombined with application of other substances as cytostatic drugs,growth factor inhibitors, cell cycle blockers, angiogenesis inhibitorsor other antibodies to determine synergistic efficacy and potentialtoxicity of combinations. To analyze toxic side effects mediated byantibodies of the invention animals can be inoculated with antibodies orcontrol reagents and thoroughly investigated for symptoms possiblyrelated to GT468-antibody therapy. Possible side effects of in vivoapplication of GT468 antibodies particularly include toxicity at GT468expressing tissues including placenta. Antibodies recognizing GT468 inhuman and in other species, e.g. mice, are particularly useful topredict potential side effects mediated by application of monoclonalGT468-antibodies in humans.

Epitope Mapping

Mapping of epitopes recognized by antibodies of invention can beperformed as described in detail in “Epitope Mapping Protocols (Methodsin Molecular Biology) by Glenn E. Morris ISBN-089603-375-9 and in“Epitope Mapping: A Practical Approach” Practical Approach Series, 248by Olwyn M. R. Westwood, Frank C. Hay.

I. Bispecific/Multispecific Molecules which Bind to GT468

In yet another embodiment of the invention, antibodies to GT468 can bederivatized or linked to another functional molecule, e.g., anotherpeptide or protein (e.g., an Fab′ fragment) to generate a bispecific ormultispecific molecule which binds to multiple binding sites or targetepitopes. For example, an antibody of the invention can be functionallylinked (e.g. by chemical coupling, genetic fusion, noncovalentassociation or otherwise) to one or more other binding molecules, suchas another antibody, peptide or binding mimetic.

Accordingly, the present invention includes bispecific and multispecificmolecules comprising at least one first binding specificity for GT468and a second binding specificity for a second target epitope. In aparticular embodiment of the invention, the second target epitope is anFc receptor, e.g. human Fc-gammaRI (CD64) or a human Fc-alpha receptor(CD89), or a T cell receptor, e.g. CD3. Therefore, the inventionincludes bispecific and multispecific molecules capable of binding bothto Fc-gammaR, Fc-alphaR or Fc-epsilonR expressing effector cells (e.g.monocytes, macrophagesor polymorphonuclear cells (PMNs)), and to targetcells expressing GT468 and/or being characterized by association ofGT468 with their cell surface. These bispecific and multispecificmolecules may target cells expressing GT468 and/or being characterizedby association of GT468 with their cell surface to effector cells andmay trigger Fc receptor-mediated effector cell activities, such asphagocytosis of cells expressing GT468 and/or being characterized byassociation of GT468 with their cell surface, antibody dependentcellular cytotoxicity (ADCC), cytokine release, or generation ofsuperoxide anion.

Bispecific and multispecific molecules of the invention can furtherinclude a third binding specificity, in addition to an anti-Fc bindingspecificity and an anti-GT468 binding specificity. In one embodiment,the third binding specificity is an anti-enhancement factor (EF)portion, e.g. a molecule which binds to a surface protein involved incytotoxic activity and thereby increases the immune response against thetarget cell. The “anti-enhancement factor portion” can be an antibody,functional antibody fragment or a ligand that binds to a given molecule,e.g., an antigen or a receptor, and thereby results in an enhancement ofthe effect of the binding determinants for the Fc receptor or targetcell antigen. The “anti-enhancement factor portion” can bind an Fcreceptor or a target cell antigen. Alternatively, the anti-enhancementfactor portion can bind to an entity that is different from the entityto which the first and second binding specificities bind. For example,the anti-enhancement factor portion can bind a cytotoxic T cell (e.g.,via CD2, CD3, CD8, CD28, CD4, CD40, ICAM-1 or other immune cell thatresults in an increased immune response against the target cell).

In one embodiment, the bispecific and multispecific molecules of theinvention comprise as a binding specificity at least one antibody,including, e.g., an Fab, Fab′, F(ab′)₂, Fv, or a single chain Fv. Theantibody may also be a light chain or heavy chain dimer, or any minimalfragment thereof such as a Fv or a single chain construct as describedin Ladner et al., U.S. Pat. No. 4,946,778. The antibody may also be abinding-domain immunoglobulin fusion protein as disclosed inUS2003/0118592 and US 2003/0133939.

In one embodiment bispecific and multispecific molecules of theinvention comprise a binding specificity for an Fc-gammaR or anFc-alphaR present on the surface of an effector cell, and a secondbinding specificity for a target cell antigen, e.g., GT468.

In one embodiment, the binding specificity for an Fc receptor isprovided by a monoclonal antibody, the binding of which is not blockedby human immunoglobulin G (IgG). As used herein, the term “IgG receptor”refers to any of the eight gamma-chain genes located on chromosome 1.These genes encode a total of twelve transmembrane or soluble receptorisoforms which are grouped into three Fc-gamma receptor classes:Fc-gammaRI (CD64), Fc-gammaRII (CD32), and Fc-gammaRIII (CD16). In onepreferred embodiment, the Fc-gamma receptor is a human high affinityFc-gammaRI.

The production and characterization of these preferred monoclonalantibodies are described by Fanger et al. in WO 88/00052 and in U.S.Pat. No. 4,954,617. These antibodies bind to an epitope of Fc-gammaRI,Fc-gammaRII or Fc-gammayRIII at a site which is distinct from the Fcγbinding site of the receptor and, thus, their binding is not blockedsubstantially by physiological levels of IgG. Specific anti-Fc-gammaRIantibodies useful in this invention are mAb 22, mAb 32, mAb 44, mAb 62and mAb 197. In other embodiments, the anti-Fcγ receptor antibody is ahumanized form of monoclonal antibody 22 (H22). The production andcharacterization of the H22 antibody is described in Graziano, R. F. etal. (1995) J. Immunol. 155 (10): 4996-5002 and WO 94/10332. The H22antibody producing cell line was deposited at the American Type CultureCollection on Nov. 4, 1992 under the designation HA022CL1 and has theaccession No. CRL 11177.

In still other preferred embodiments, the binding specificity for an Fcreceptor is provided by an antibody that binds to a human IgA receptor,e.g., an Fc-alpha receptor (Fc-alphaRI (CD89)), the binding of which ispreferably not blocked by human immunoglobulin A (IgA). The term “IgAreceptor” is intended to include the gene product of one alpha-gene(Fc-alphaRI) located on chromosome 19. This gene is known to encodeseveral alternatively spliced transmembrane isoforms of 55 to 110 kDa.Fc-alphaRI (CD89) is constitutively expressed on monocytes/macrophages,eosinophilic and neutrophilic granulocytes, but not on non-effector cellpopulations. Fc-alphaRI has medium affinity for both IgA1 and IgA2,which is increased upon exposure to cytokines such as G-CSF or GM-CSF(Morton, H. C. et al. (1996) Critical Reviews in Immunology 16:423-440). Four Fc-alphaRI-specific monoclonal antibodies, identified asA3, A59, A62 and A77, which bind Fc-alphaRI outside the IgA ligandbinding domain, have been described (Monteiro, R. C. et al. (1992) J.Immunol. 148: 1764).

Fc-alphaRI and Fc-gammaRI are preferred trigger receptors for use in theinvention because they (1) are expressed primarily on immune effectorcells, e.g., monocytes, PMNs, macrophages and dendritic cells; (2) areexpressed at high levels (e.g., 5,000-100,000 per cell); (3) aremediators of cytotoxic activities (e.g., ADCC, phagocytosis); (4)mediate enhanced antigen presentation of antigens, includingself-antigens, targeted to them.

In another embodiment the bispecific molecule is comprised of twomonoclonal antibodies according to the invention which havecomplementary functional activities, such as one antibody predominatelyworking by inducing CDC and the other antibody predominately working byinducing apoptosis.

An “effector cell specific antibody” as used herein refers to anantibody or functional antibody fragment that binds the Fc receptor ofeffector cells. Preferred antibodies for use in the subject inventionbind the Fc receptor of effector cells at a site which is not bound byendogenous immunoglobulin.

As used herein, the term “effector cell” refers to an immune cell whichis involved in the effector phase of an immune response, as opposed tothe cognitive and activation phases of an immune response. Exemplaryimmune cells include cells of myeloid or lymphoid origin, e.g,lymphocytes (e.g., B cells and T cells including cytolytic T cells(CTLs), killer cells, natural killer cells, macrophages, monocytes,eosinophils, neutrophils, polymorphonuclear cells, granulocytes, mastcells, and basophils. Some effector cells express specific Fc receptorsand carry out specific immune functions. In preferred embodiments, aneffector cell is capable of inducing antibody-dependent cellularcytotoxicity (ADCC), e.g., a neutrophil capable of inducing ADCC. Forexample, monocytes, macrophages, which express FcR are involved inspecific killing of target cells and presenting antigens to othercomponents of the immune system, or binding to cells that presentantigens. In other embodiments, an effector cell can phagocytose atarget antigen, target cell, or microorganism. The expression of aparticular FcR on an effector cell can be regulated by humoral factorssuch as cytokines. For example, expression of Fc-gammaRI has been foundto be up-regulated by interferon gamma (IFN-γ). This enhanced expressionincreases the cytotoxic activity of Fc-gammaRI-bearing cells againsttargets. An effector cell can phagocytose or lyse a target antigen or atarget cell.

“Target cell” shall mean any undesirable cell in a subject (e.g., ahuman or animal) that can be targeted by an antibody of the invention.In preferred embodiments, the target cell is a cell expressing oroverexpressing GT468 and/or being characterized by association of GT468with its cell surface. Cells expressing GT468 and/or being characterizedby association of GT468 with their cell surface typically include tumorcells.

Bispecific and multispecific molecules of the present invention can bemade using chemical techniques (see e.g., D. M. Kranz et al. (1981)Proc. Natl. Acad. Sci. USA 78:5807), “polydoma” techniques (See U.S.Pat. No. 4,474,893, to Reading), or recombinant DNA techniques.

In particular, bispecific and multispecific molecules of the presentinvention can be prepared by conjugating the constituent bindingspecificities, e.g., the anti-FcR and anti-GT468 binding specificities,using methods known in the art. For example, each binding specificity ofthe bispecific and multispecific molecule can be generated separatelyand then conjugated to one another. When the binding specificities areproteins or peptides, a variety of coupling or cross-linking agents canbe used for covalent conjugation. Examples of cross-linking agentsinclude protein A, carbodiimide, N-succinimidyl-5-acetyl-thioacetate(SATA), 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB),o-phenylenedimaleimide (oPDM),N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP), andsulfosuccinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate(sulfo-SMCC) (see e.g., Karpovsky et al. (1984) J. Exp. Med. 160: 1686;Liu, M A et al. (1985) Proc. Natl. Acad. Sci. USA 82: 8648). Othermethods include those described by Paulus (Behring Ins. Mitt. (1985) No.78, 118-132); Brennan et al. (Science (1985) 229: 81-83), and Glennie etal. (J. Immunol. (1987) 139: 2367-2375). Preferred conjugating agentsare SATA and sulfo-SMCC, both available from Pierce Chemical Co.(Rockford, Ill.).

When the binding specificities are antibodies, they can be conjugatedvia sulfhydryl bonding of the C-terminus hinge regions of the two heavychains. In a particularly preferred embodiment, the hinge region ismodified to contain an odd number of sulfhydryl residues, preferablyone, prior to conjugation.

Alternatively, both binding specificities can be encoded in the samevector and expressed and assembled in the same host cell. This method isparticularly useful where the bispecific and multispecific molecule is amAb×mAb, mAb×Fab, Fab×F(ab′)₂ or ligand×Fab fusion protein. A bispecificand multispecific molecule of the invention, e.g., a bispecificmolecule, can be a single chain molecule, such as a single chainbispecific antibody, a single chain bispecific molecule comprising onesingle chain antibody and a binding determinant, or a single chainbispecific molecule comprising two binding determinants. Bispecific andmultispecific molecules can also be single chain molecules or maycomprise at least two single chain molecules. Methods for preparing bi-and multispecific molecules are described for example in U.S. Pat. No.5,260,203; U.S. Pat. No. 5,455,030; U.S. Pat. No. 4,881,175; U.S. Pat.No. 5,132,405; U.S. Pat. No. 5,091,513; U.S. Pat. No. 5,476,786; U.S.Pat. No. 5,013,653; U.S. Pat. No. 5,258,498; and U.S. Pat. No.5,482,858.

Binding of the bispecific and multispecific molecules to their specifictargets can be confirmed by enzyme-linked immunosorbent assay (ELISA), aradioimmunoassay (RIA), FACS analysis, a bioassay (e.g., growthinhibition), or a Western Blot Assay. Each of these assays generallydetects the presence of protein-antibody complexes of particularinterest by employing a labeled reagent (e.g., an antibody) specific forthe complex of interest. For example, the FcR-antibody complexes can bedetected using e.g., an enzyme-linked antibody or antibody fragmentwhich recognizes and specifically binds to the antibody-FcR complexes.Alternatively, the complexes can be detected using any of a variety ofother immunoassays. For example, the antibody can be radioactivelylabeled and used in a radioimmunoassay (RIA) (see, for example,Weintraub, B., Principles of Radioimmunoassays, Seventh Training Courseon Radioligand Assay Techniques, The Endocrine Society, March, 1986).The radioactive isotope can be detected by such means as the use of aγ-counter or a scintillation counter or by autoradiography.

II. Immunoconjugates

In another aspect, the present invention features an anti-GT468 antibodyconjugated to a therapeutic moiety or agent, such as a cytotoxin, a drug(e.g., an immunosuppressant) or a radioisotope. Such conjugates arereferred to herein as “immunoconjugates”. Immunoconjugates which includeone or more cytotoxins are referred to as “immunotoxins”. A cytotoxin orcytotoxic agent includes any agent that is detrimental to and, inparticular, kills cells. Examples include taxol, cytochalasin B,gramicidin D, ethidium bromide, emetine, mitomycin, etoposide,tenoposide, vincristine, vinblastine, colchicin, doxorubicin,daunorubicin, dihydroxy anthracin dione, mitoxantrone, mithramycin,actinomycin D, 1-dehydrotestosterone, glucocorticoids, procaine,tetracaine, lidocaine, propranolol, and puromycin and analogs orhomologs thereof.

Suitable therapeutic agents for forming immunoconjugates of theinvention include, but are not limited to, antimetabolites (e.g.,methotrexate, 6-mercaptopurine, 6-thioguanine, cytarabine, fludarabin,5-fluorouracil decarbazine), alkylating agents (e.g., mechlorethamine,thioepa chlorambucil, melphalan, carmustine (BSNU) and lomustine (CCNU),cyclophosphamide, busulfan, dibromomannitol, streptozotocin, mitomycinC, and cis-dichlorodiamine platinum (II) (DDP) cisplatin),anthracyclines (e.g., daunorubicin (formerly daunomycin) anddoxorubicin), antibiotics (e.g., dactinomycin (formerly actinomycin),bleomycin, mithramycin, and anthramycin (AMC), and anti-mitotic agents(e.g., vincristine and vinblastine). In a preferred embodiment, thetherapeutic agent is a cytotoxic agent or a radiotoxic agent. In anotherembodiment, the therapeutic agent is an immunosuppressant. In yetanother embodiment, the therapeutic agent is GM-CSF. In a preferredembodiment, the therapeutic agent is doxorubicin, cisplatin, bleomycin,sulfate, carmustine, chlorambucil, cyclophosphamide or ricin A.

Antibodies of the present invention also can be conjugated to aradioisotope, e.g., iodine-131, yttrium-90 or indium-111, to generatecytotoxic radiopharmaceuticals for treating a GT468-related disorder,such as a cancer. The antibody conjugates of the invention can be usedto modify a given biological response, and the drug moiety is not to beconstrued as limited to classical chemical therapeutic agents. Forexample, the drug moiety may be a protein or polypeptide possessing adesired biological activity. Such proteins may include, for example, anenzymatically active toxin, or active fragment thereof, such as abrin,ricin A, pseudomonas exotoxin, or diphtheria toxin; a protein such astumor necrosis factor or interferon-γ; or, biological response modifierssuch as, for example, lymphokines, interleukin-1 (“IL-1”), interleukin-2(“IL-2”), interleukin-6 (“IL-6”), granulocyte macrophage colonystimulating factor (“GM-CSF”), granulocyte colony stimulating factor(“G-CSF”), or other growth factors.

Techniques for conjugating such therapeutic moiety to antibodies arewell known, see, e.g., Amon et al., “Monoclonal Antibodies ForImmunotargeting Of Drugs In Cancer Therapy”, in Monoclonal AntibodiesAnd Cancer Therapy, Reisfeld et al. (eds.), pp. 243-56 (Alan R. Liss,Inc. 1985); Hellstrom et al., “Antibodies For Drug Delivery”, inControlled Drug Delivery (2nd Ed.), Robinson et al. (eds.), pp. 623-53(Marcel Dekker, Inc. 1987); Thorpe, “Antibody Carriers Of CytotoxicAgents In Cancer Therapy: A Review”, in Monoclonal Antibodies '84:Biological And Clinical Applications, Pinchera et al. (eds.), pp.475-506 (1985); “Analysis, Results, And Future Prospective Of TheTherapeutic Use Of Radiolabeled Antibody In Cancer Therapy”, inMonoclonal Antibodies For Cancer Detection And Therapy, Baldwin et al.(eds.), pp. 303-16 (Academic Press 1985), and Thorpe et al., “ThePreparation And Cytotoxic Properties Of Antibody-Toxin Conjugates”,Immunol. Rev., 62: 119-58 (1982).

In a further embodiment, the antibodies according to the invention areattached to a linker-chelator, e.g., tiuxetan, which allows for theantibody to be conjugated to a radioisotope.

III. Pharmaceutical Compositions

In another aspect, the present invention provides a composition, e.g., apharmaceutical composition, containing one or a combination ofantibodies of the present invention. The pharmaceutical compositions maybe formulated with pharmaceutically acceptable carriers or diluents aswell as any other known adjuvants and excipients in accordance withconventional techniques such as those disclosed in Remington: TheScience and Practice of Pharmacy, 19th Edition, Gennaro, Ed., MackPublishing Co., Easton, Pa., 1995. In one embodiment, the compositionsinclude a combination of multiple (e.g., two or more) isolatedantibodies of the invention which act by different mechanisms, e.g., oneantibody which predominately acts by inducing CDC in combination withanother antibody which predominately acts by inducing apoptosis.

Pharmaceutical compositions of the invention also can be administered incombination therapy, i.e., combined with other agents. For example, thecombination therapy can include a composition of the present inventionwith at least one anti-inflammatory agent or at least oneimmunosuppressive agent. In one embodiment such therapeutic agentsinclude one or more anti-inflammatory agents, such as a steroidal drugor a NSAID (nonsteroidal anti-inflammatory drug). Preferred agentsinclude, for example, aspirin and other salicylates, Cox-2 inhibitors,such as rofecoxib (Vioxx) and celecoxib (Celebrex), NSAIDs such asibuprofen (Motrin, Advil), fenoprofen (Nalfon), naproxen (Naprosyn),sulindac (Clinoril), diclofenac (Voltaren), piroxicam (Feldene),ketoprofen (Orudis), diflunisal (Dolobid), nabumetone (Relafen),etodolac (Lodine), oxaprozin (Daypro), and indomethacin (Indocin).

In another embodiment, such therapeutic agents include agents leading tothe depletion or functional inactivation of regulatory T cells like lowdose cyclophosphamid, anti-CTLA4 antibodies, anti-IL2 oranti-IL2-receptor antibodies.

In yet another embodiment, such therapeutic agents include one or morechemotherapeutics, such as Taxol derivatives, taxotere, gemcitabin,5-Fluoruracil, doxorubicin (Adriamycin), cisplatin (Platinol),cyclophosphamide (Cytoxan, Procytox, Neosar). In another embodiment,antibodies of the present invention may be administered in combinationwith chemotherapeutic agents, which preferably show therapeutic efficacyin patients suffering from breast, lung, gastric and/or ovarian cancer,or other cancer types e.g. as described herein.

In yet another embodiment, the antibodies of the invention may beadministered in conjunction with radiotherapy and/or autologousperipheral stem cell or bone marrow transplantation.

In still another embodiment, the antibodies of the invention may beadministered in combination with one or more antibodies selected fromanti-CD25 antibodies, anti-EPCAM antibodies, anti-EGFR, anti-Her2/neu,and anti-CD40 antibodies.

In yet a further embodiment, the antibodies of the invention may beadministered in combination with an anti-C3b(i) antibody in order toenhance complement activation.

As used herein, “pharmaceutically acceptable carrier” includes any andall solvents, dispersion media, coatings, antibacterial and antifungalagents, isotonic and absorption delaying agents, and the like that arephysiologically compatible. Preferably, the carrier is suitable forintravenous, intramuscular, subcutaneous, parenteral, spinal orepidermal administration (e.g., by injection or infusion). Depending onthe route of administration, the active compound, i.e., antibody,bispecific and multispecific molecule, may be coated in a material toprotect the compound from the action of acids and other naturalconditions that may inactivate the compound.

A “pharmaceutically acceptable salt” refers to a salt that retains thedesired biological activity of the parent compound and does not impartany undesired toxicological effects (see e.g., Berge, S. M., et al.(1977) J. Pharm. Sci. 66: 1-19).

Examples of such salts include acid addition salts and base additionsalts. Acid addition salts include those derived from nontoxic inorganicacids, such as hydrochloric, nitric, phosphoric, sulfuric, hydrobromic,hydroiodic, phosphorous and the like, as well as from nontoxic organicacids such as aliphatic mono- and dicarboxylic acids, phenyl-substitutedalkanoic acids, hydroxy alkanoic acids, aromatic acids, aliphatic andaromatic sulfonic acids and the like. Base addition salts include thosederived from alkaline earth metals, such as sodium, potassium,magnesium, calcium and the like, as well as from nontoxic organicamines, such as N,N′-dibenzylethylenediamine, N-methylglucamine,chloroprocaine, choline, diethanolamine, ethylenediamine, procaine andthe like.

A composition of the present invention can be administered by a varietyof methods known in the art. As will be appreciated by the skilledartisan, the route and/or mode of administration will vary dependingupon the desired results. The active compounds can be prepared withcarriers that will protect the compound against rapid release, such as acontrolled release formulation, including implants, transdermal patches,and microencapsulated delivery systems. Biodegradable, biocompatiblepolymers can be used, such as ethylene vinyl acetate, polyanhydrides,polyglycolic acid, collagen, polyorthoesters, and polylactic acid.Methods for the preparation of such formulations are generally known tothose skilled in the art. See, e.g., Sustained and Controlled ReleaseDrug Delivery Systems, J. R. Robinson, ed., Marcel Dekker, Inc., NewYork, 1978.

To administer a compound of the invention by certain routes ofadministration, it may be necessary to coat the compound with, orco-administer the compound with, a material to prevent its inactivation.For example, the compound may be administered to a subject in anappropriate carrier, for example, liposomes, or a diluent.Pharmaceutically acceptable diluents include saline and aqueous buffersolutions. Liposomes include water-in-oil-in-water CGF emulsions as wellas conventional liposomes (Strejan et al. (1984) J. Neuroimmunol. 7:27).

Pharmaceutically acceptable carriers include sterile aqueous solutionsor dispersions and sterile powders for the extemporaneous preparation ofsterile injectable solutions or dispersions. The use of such media andagents for pharmaceutically active substances is known in the art.Except insofar as any conventional media or agent is incompatible withthe active compound, use thereof in the pharmaceutical compositions ofthe invention is contemplated. Supplementary active compounds can alsobe incorporated into the compositions.

Therapeutic compositions typically must be sterile and stable under theconditions of manufacture and storage. The composition can be formulatedas a solution, microemulsion, liposome, or other ordered structuresuitable to high drug concentration. The carrier can be a solvent ordispersion medium containing, for example, water, ethanol, polyol (forexample, glycerol, propylene glycol, and liquid polyethylene glycol, andthe like), and suitable mixtures thereof. The proper fluidity can bemaintained, for example, by the use of a coating such as lecithin, bythe maintenance of the required particle size in the case of dispersionand by the use of surfactants. In many cases, it will be preferable toinclude isotonic agents, for example, sugars, polyalcohols such asmannitol, sorbitol, or sodium chloride in the composition. Prolongedabsorption of the injectable compositions can be brought about byincluding in the composition an agent that delays absorption, forexample, monostearate salts and gelatin.

Sterile injectable solutions can be prepared by incorporating the activecompound in the required amount in an appropriate solvent with one or acombination of ingredients enumerated above, as required, followed bysterilization microfiltration.

Generally, dispersions are prepared by incorporating the active compoundinto a sterile vehicle that contains a basic dispersion medium and therequired other ingredients from those enumerated above. In the case ofsterile powders for the preparation of sterile injectable solutions, thepreferred methods of preparation are vacuum drying and freeze-drying(lyophilization) that yield a powder of the active ingredient plus anyadditional desired ingredient from a previously sterile-filteredsolution thereof.

Dosage regimens are adjusted to provide the optimum desired response(e.g., a therapeutic response). For example, a single bolus may beadministered, several divided doses may be administered over time or thedose may be proportionally reduced or increased as indicated by theexigencies of the therapeutic situation. It is especially advantageousto formulate parenteral compositions in dosage unit form for ease ofadministration and uniformity of dosage. Dosage unit form as used hereinrefers to physically discrete units suited as unitary dosages for thesubjects to be treated; each unit contains a predetermined quantity ofactive compound calculated to produce the desired therapeutic effect inassociation with the required pharmaceutical carrier. The specificationfor the dosage unit forms of the invention are dictated by and directlydependent on (a) the unique characteristics of the active compound andthe particular therapeutic effect to be achieved, and (b) thelimitations inherent in the art of compounding such an active compoundfor the treatment of sensitivity in individuals.

Examples of pharmaceutically-acceptable antioxidants include: (1) watersoluble antioxidants, such as ascorbic acid, cysteine hydrochloride,sodium bisulfate, sodium metabisulfite, sodium sulfite and the like; (2)oil-soluble antioxidants, such as ascorbyl palmitate, butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propylgallate, alpha-tocopherol, and the like; and (3) metal chelating agents,such as citric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol,tartaric acid, phosphoric acid, and the like.

For the therapeutic compositions, formulations of the present inventioninclude those suitable for oral, nasal, topical (including buccal andsublingual), rectal, vaginal and/or parenteral administration. Theformulations may conveniently be presented in unit dosage form and maybe prepared by any methods known in the art of pharmacy. The amount ofactive ingredient which can be combined with a carrier material toproduce a single dosage form will vary depending upon the subject beingtreated, and the particular mode of administration. The amount of activeingredient which can be combined with a carrier material to produce asingle dosage form will generally be that amount of the compositionwhich produces a therapeutic effect.

Generally, out of one hundred percent, this amount will range from about0.01 percent to about ninety-nine percent of active ingredient,preferably from about 0.1 percent to about 70 percent, most preferablyfrom about 1 percent to about 30 percent.

Formulations of the present invention which are suitable for vaginaladministration also include pessaries, tampons, creams, gels, pastes,foams or spray formulations containing such carriers as are known in theart to be appropriate. Dosage forms for the topical or transdermaladministration of compositions of this invention include powders,sprays, ointments, pastes, creams, lotions, gels, solutions, patches andinhalants. The active compound may be mixed under sterile conditionswith a pharmaceutically acceptable carrier, and with any preservatives,buffers, or propellants which may be required.

The phrases “parenteral administration” and “administered parenterally”as used herein means modes of administration other than enteral andtopical administration, usually by injection, and includes, withoutlimitation, intravenous, intramuscular, intraarterial, intrathecal,intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal,transtracheal, subcutaneous, subcuticular, intraarticular, subcapsular,subarachnoid, intraspinal, epidural and intrasternal injection andinfusion.

Examples of suitable aqueous and nonaqueous carriers which may beemployed in the pharmaceutical compositions of the invention includewater, ethanol, polyols (such as glycerol, propylene glycol,polyethylene glycol, and the like), and suitable mixtures thereof,vegetable oils, such as olive oil, and injectable organic esters, suchas ethyl oleate. Proper fluidity can be maintained, for example, by theuse of coating materials, such as lecithin, by the maintenance of therequired particle size in the case of dispersions, and by the use ofsurfactants.

These compositions may also contain adjuvants such as preservatives,wetting agents, emulsifying agents and dispersing agents. Prevention ofthe presence of microorganisms may be ensured both by sterilizationprocedures, and by the inclusion of various antibacterial and antifungalagents, for example, paraben, chlorobutanol, phenol sorbic acid, and thelike. It may also be desirable to include isotonic agents, such assugars, sodium chloride, and the like into the compositions. Inaddition, prolonged absorption of the injectable pharmaceutical form maybe brought about by the inclusion of agents which delay absorption suchas aluminum monostearate and gelatin.

In one embodiment the monoclonal antibodies of the invention areadministered in crystalline form by subcutaneous injection, cf. Yang etal. (2003) PNAS, 100 (12): 6934-6939. When the compounds of the presentinvention are administered as pharmaceuticals, to humans and animals,they can be given alone or as a pharmaceutical composition containing,for example, 0.01 to 99.5% (more preferably, 0.1 to 90%) of activeingredient in combination with a pharmaceutically acceptable carrier.

Regardless of the route of administration selected, the compounds of thepresent invention, which may be used in a suitable hydrated form, and/orthe pharmaceutical compositions of the present invention, are formulatedinto pharmaceutically acceptable dosage forms by conventional methodsknown to those of skill in the art.

Actual dosage levels of the active ingredients in the pharmaceuticalcompositions of the present invention may be varied so as to obtain anamount of the active ingredient which is effective to achieve thedesired therapeutic response for a particular patient, composition, andmode of administration, without being toxic to the patient. The selecteddosage level will depend upon a variety of pharmacokinetic factorsincluding the activity of the particular compositions of the presentinvention employed, the route of administration, the time ofadministration, the rate of excretion of the particular compound beingemployed, the duration of the treatment, other drugs, compounds and/ormaterials used in combination with the particular compositions employed,the age, sex, weight, condition, general health and prior medicalhistory of the patient being treated, and like factors well known in themedical arts.

A physician or veterinarian having ordinary skill in the art can readilydetermine and prescribe the effective amount of the pharmaceuticalcomposition required. For example, the physician or veterinarian couldstart doses of the compounds of the invention employed in thepharmaceutical composition at levels lower than that required in orderto achieve the desired therapeutic effect and gradually increase thedosage until the desired effect is achieved. In general, a suitabledaily dose of a composition of the invention will be that amount of thecompound which is the lowest dose effective to produce a therapeuticeffect. Such an effective dose will generally depend upon the factorsdescribed above. It is preferred that administration be intravenous,intramuscular, intraperitoneal, or subcutaneous, preferably administeredproximal to the site of the target. If desired, the effective daily doseof a therapeutic composition may be administered as two, three, four,five, six or more sub-doses administered separately at appropriateintervals throughout the day, optionally, in unit dosage forms. While itis possible for a compound of the present invention to be administeredalone, it is preferable to administer the compound as a pharmaceuticalformulation (composition).

In one embodiment, the antibodies of the invention may be administeredby infusion, preferably slow continuous infusion over a long period,such as more than 24 hours, in order to reduce toxic side effects. Theadministration may also be performed by continuous infusion over aperiod of from 2 to 24 hours, such as of from 2 to 12 hours. Suchregimen may be repeated one or more times as necessary, for example,after 6 months or 12 months. The dosage can be determined or adjusted bymeasuring the amount of circulating monoclonal anti-GT468 antibodiesupon administration in a biological sample by using anti-idiotypicantibodies which target the anti-GT468 antibodies.

In yet another embodiment, the antibodies are administered bymaintenance therapy, such as, e.g., once a week for a period of 6 monthsor more.

In still another embodiment, the antibodies according to the inventionmay be administered by a regimen including one infusion of an antibodyagainst GT468 followed by an infusion of an antibody against GT468conjugated to a radioisotope. The regimen may be repeated, e.g., 7 to 9days later.

Therapeutic compositions can be administered with medical devices knownin the art. For example, in a preferred embodiment, a therapeuticcomposition of the invention can be administered with a needlelesshypodermic injection device, such as the devices disclosed in U.S. Pat.No. 5,399,163; U.S. Pat. No. 5,383,851; U.S. Pat. No. 5,312,335; U.S.Pat. No. 5,064,413; U.S. Pat. No. 4,941,880; U.S. Pat. No. 4,790,824; orU.S. Pat. No. 4,596,556. Examples of well-known implants and modulesuseful in the present invention include those described in: U.S. Pat.No. 4,487,603, which discloses an implantable micro-infusion pump fordispensing medication at a controlled rate; U.S. Pat. No. 4,486,194,which discloses a therapeutic device for administering medicants throughthe skin; U.S. Pat. No. 4,447,233, which discloses a medication infusionpump for delivering medication at a precise infusion rate; U.S. Pat. No.4,447,224, which discloses a variable flow implantable infusionapparatus for continuous drug delivery; U.S. Pat. No. 4,439,196, whichdiscloses an osmotic drug delivery system having multi-chambercompartments; and U.S. Pat. No. 4,475,196, which discloses an osmoticdrug delivery system.

Many other such implants, delivery systems, and modules are known tothose skilled in the art. In certain embodiments, the antibodies of theinvention can be formulated to ensure proper distribution in vivo. Forexample, the blood-brain barrier (BBB) excludes many highly hydrophiliccompounds. To ensure that the therapeutic compounds of the inventioncross the BBB (if desired), they can be formulated, for example, inliposomes. For methods of manufacturing liposomes, see, e.g., U.S. Pat.No. 4,522,811; U.S. Pat. No. 5,374,548; and U.S. Pat. No. 5,399,331. Theliposomes may comprise one or more moieties which are selectivelytransported into specific cells or organs, and thus enhance targeteddrug delivery (see, e.g., V. V. Ranade (1989) J. Clin. Pharmacol. 29:685). Exemplary targeting moieties include folate or biotin (see, e.g.,U.S. Pat. No. 5,416,016 to Low et al.); mannosides (Umezawa et al.,(1988) Biochem. Biophys. Res. Commun. 153: 1038); antibodies (P. G.Bloeman et al. (1995) FEBS Lett. 357: 140; M. Owais et al. (1995)Antimicrob. Agents Chemother. 39: 180); and surfactant protein Areceptor (Briscoe et al. (1995) Am. J. Physiol. 1233: 134).

In one embodiment of the invention, the therapeutic compounds of theinvention are formulated in liposomes. In a more preferred embodiment,the liposomes include a targeting moiety. In a most preferredembodiment, the therapeutic compounds in the liposomes are delivered bybolus injection to a site proximal to the desired area, e.g., the siteof a tumor. The composition must be fluid to the extent that easysyringability exists. It must be stable under the conditions ofmanufacture and storage and must be preserved against the contaminatingaction of microorganisms such as bacteria and fungi.

In a further embodiment, antibodies of the invention can be formulatedto prevent or reduce their transport across the placenta. This can bedone by methods known in the art, e.g., by PEGylation of the antibodiesor by use of F(ab)2′ fragments. Further references can be made to“Cunningham-Rundles C, Zhuo Z, Griffith B, Keenan J. (1992) Biologicalactivities of polyethylene-glycol immunoglobulin conjugates. Resistanceto enzymatic degradation. J. Immunol. Methods, 152: 177-190; and to“Landor M. (1995) Maternal-fetal transfer of immunoglobulins, AnnAllergy Asthma Immunol. 74: 279-283.

A “therapeutically effective dosage” for tumor therapy can be measuredby objective tumor responses which can either be complete or partial. Acomplete response (CR) is defined as no clinical, radiological or otherevidence of disease. A partial response (PR) results from a reduction inaggregate tumor size of greater than 50%. Median time to progression isa measure that characterizes the durability of the objective tumorresponse.

A “therapeutically effective dosage” for tumor therapy can also bemeasured by its ability to stabilize the progression of disease. Theability of a compound to inhibit cancer can be evaluated in an animalmodel system predictive of efficacy in human tumors. Alternatively, thisproperty of a composition can be evaluated by examining the ability ofthe compound to inhibit cell growth or apoptosis by in vitro assaysknown to the skilled practitioner. A therapeutically effective amount ofa therapeutic compound can decrease tumor size, or otherwise amelioratesymptoms in a subject. One of ordinary skill in the art would be able todetermine such amounts based on such factors as the subject's size, theseverity of the subject's symptoms, and the particular composition orroute of administration selected.

The composition must be sterile and fluid to the extent that thecomposition is deliverable by syringe. In addition to water, the carriercan be an isotonic buffered saline solution, ethanol, polyol (forexample, glycerol, propylene glycol, and liquid polyethylene glycol, andthe like), and suitable mixtures thereof. Proper fluidity can bemaintained, for example, by use of coating such as lecithin, bymaintenance of required particle size in the case of dispersion and byuse of surfactants. In many cases, it is preferable to include isotonicagents, for example, sugars, polyalcohols such as mannitol or sorbitol,and sodium chloride in the composition. Long-term absorption of theinjectable compositions can be brought about by including in thecomposition an agent which delays absorption, for example, aluminummonostearate or gelatin.

When the active compound is suitably protected, as described above, thecompound may be orally administered, for example, with an inert diluentor an assimilable edible carrier.

IV. Uses and Methods of the Invention

The antibodies (including immunoconjugates, bispecifics/multispecifics,compositions and other derivatives described herein) of the presentinvention have numerous therapeutic utilities involving the treatment ofdisorders involving cells expressing GT468 and/or being characterized byassociation of GT468 with their cell surface. For example, theantibodies can be administered to cells in culture, e.g., in vitro or exvivo, or to human subjects, e.g., in vivo, to treat or prevent a varietyof disorders such as those described herein. As used herein, the term“subject” is intended to include human and non-human animals whichrespond to the antibodies against GT468. Preferred subjects includehuman patients having disorders that can be corrected or ameliorated bykilling diseased cells, in particular cells characterized by an alteredexpression pattern of GT468 and/or an altered pattern of association ofGT468 with their cell surface compared to normal cells.

A therapeutic effect in the treatments discussed herein is preferablyachieved through the functional properties of the antibodies of theinvention to mediate killing of cells e.g. by inducing complementdependent cytotoxicity (CDC) mediated lysis, antibody dependent cellularcytotoxicity (ADCC) mediated lysis, apoptosis, homotypic adhesion,and/or phagocytosis, preferably by inducing CDC mediated lysis and/orADCC mediated lysis.

For example, in one embodiment, antibodies of the present invention canbe used to treat a subject with a tumorigenic disorder, e.g., a disordercharacterized by the presence of tumor cells expressing GT468 and/orbeing characterized by association of GT468 with their cell surfaceincluding, for example, breast cancer. Examples of tumorigenic diseaseswhich can be treated and/or prevented encompass all GT468 expressingcancers and tumor entities including breast cancer, lung cancer, gastriccancer, ovarian cancer, hepatocellular cancer, colon cancer, pancreaticcancer, esophageal cancer, head & neck cancer, kidney cancer, prostatecancer, and liver cancer. These cancers may be in early, intermediate oradvanced stages, e.g. metastasis.

The pharmaceutical compositions and methods of treatment describedaccording to the invention may also be used for immunization orvaccination to prevent a disease described herein.

In another embodiment, antibodies of the invention can be used to detectlevels of GT468 or particular forms of GT468, or levels of cells whichcontain GT468 on their membrane surface, which levels can then be linkedto certain diseases or disease symptoms such as described above.Alternatively, the antibodies can be used to deplete or interact withthe function of cells expressing GT468 and/or being characterized byassociation of GT468 with their cell surface, thereby implicating thesecells as important mediators of the disease. This can be achieved bycontacting a sample and a control sample with the anti-GT468 antibodyunder conditions that allow for the formation of a complex between theantibody and GT468. Any complexes formed between the antibody and GT468are detected and compared in the sample and a control sample, i.e. areference sample.

Antibodies of the invention can be initially tested for their bindingactivity associated with therapeutic or diagnostic uses in vitro. Forexample, the antibodies can be tested using flow cytometric assays asdescribed herein.

Moreover, activity of the antibodies in triggering at least oneeffector-mediated effector cell activity, including inhibiting thegrowth of and/or killing of cells expressing GT468 and/or beingcharacterized by association of GT468 with their cell surface, can beassayed. For example, the ability of the antibodies to trigger CDCand/or apoptosis can be assayed. Protocols for assaying for CDC,homotypic adhesion, molecular clustering or apoptosis are describedherein.

The antibodies of the invention can be used to elicit in vivo or invitro one or more of the following biological activities: to inhibit thegrowth of and/or differentiation of a cell expressing GT468 and/or beingcharacterized by association of GT468 with its cell surface; to kill acell expressing GT468 and/or being characterized by association of GT468with its cell surface; to mediate phagocytosis or ADCC of a cellexpressing GT468 and/or being characterized by association of GT468 withits cell surface in the presence of effector cells; to mediate CDC of acell expressing GT468 and/or being characterized by association of GT468with its cell surface in the presence of complement; to mediateapoptosis of a cell expressing GT468 and/or being characterized byassociation of GT468 with its cell surface; to induce homotypicadhesion; and/or to induce translocation into lipid rafts upon bindingGT468.

In a particular embodiment, the antibodies are used in vivo or in vitroto treat, prevent or diagnose a variety of GT468-related diseases.Examples of GT468-related diseases include, among others, cancers suchas breast cancer, lung cancer, gastric cancer, ovarian cancer,hepatocellular cancer, colon cancer, pancreatic cancer, esophagealcancer, head & neck cancer, kidney cancer, prostate cancer, and livercancer.

Suitable routes of administering the antibody compositions of theinvention in vivo and in vitro are well known in the art and can beselected by those of ordinary skill.

As described above, anti-GT468 antibodies of the invention can beco-administered with one or other more therapeutic agents, e.g., acytotoxic agent, a radiotoxic agent, antiangiogenic agent or andimmunosuppressive agent to reduce the induction of immune responsesagainst the antibodies of invention. The antibody can be linked to theagent (as an immunocomplex) or can be administered separate from theagent. In the latter case (separate administration), the antibody can beadministered before, after or concurrently with the agent or can beco-administered with other known therapies, e.g., an anti-cancertherapy, e.g., radiation. Such therapeutic agents include, among others,anti-neoplastic agents such as listed above. Co-administration of theanti-GT468 antibodies of the present invention with chemotherapeuticagents provides two anti-cancer agents which operate via differentmechanisms yielding a cytotoxic effect to tumor cells. Suchco-administration can solve problems due to development of resistance todrugs or a change in the antigenicity of the tumor cells which wouldrender them unreactive with the antibody.

In another particular embodiment of the invention, the subject beingadministered the antibody is additionally treated with an antiagionicagent including antibodies targeting VEGF or VEGFR and one or morechemical compounds inhibiting angiogenesis. Pretreatment with orparallel application of these drugs may improve the penetration ofantibodies in bulk tumors.

In another particular embodiment of the invention, the subject beingadministered the antibody is additionally treated with a compoundinhibiting growth factor receptor signaling including monoclonalantibodies binding to the EGFR receptor as well as chemical compoundsinhibiting signaling initiated by the EGFR, Her1 or Her2/neu receptor.

Target-specific effector cells, e.g., effector cells linked tocompositions (e.g. antibodies, multispecific and bispecific molecules)of the invention can also be used as therapeutic agents. Effector cellsfor targeting can be human leukocytes such as macrophages, neutrophilsor monocytes. Other cells include eosinophils, natural killer cells andother IgG- or IgA-receptor bearing cells. If desired, effector cells canbe obtained from the subject to be treated. The target-specific effectorcells can be administered as a suspension of cells in a physiologicallyacceptable solution. The number of cells administered can be in theorder of 10⁸ to 10⁹ but will vary depending on the therapeutic purpose.In general, the amount will be sufficient to obtain localization at thetarget cell, e.g., a tumor cell expressing GT468 and/or beingcharacterized by association of GT468 with its cell surface, and toeffect cell killing by, e.g., phagocytosis. Routes of administration canalso vary.

Therapy with target-specific effector cells can be performed inconjunction with other techniques for removal of targeted cells. Forexample, anti-tumor therapy using the compositions of the inventionand/or effector cells armed with these compositions can be used inconjunction with chemotherapy. Additionally, combination immunotherapymay be used to direct two distinct cytotoxic effector populations towardtumor cell rejection. For example, anti-GT468 antibodies linked toanti-Fc-RI or anti-CD3 may be used in conjunction with IgG- orIgA-receptor specific binding agents.

Bispecific and multispecific molecules of the invention can also be usedto modulate Fc-gammaR or Fc-alphaR levels on effector cells, such as bycapping and eliminating receptors on the cell surface. Mixtures ofanti-Fc receptors can also be used for this purpose.

The compositions (e.g., antibodies, multispecific and bispecificmolecules and immunoconjugates) of the invention which have complementbinding sites, such as portions from IgG1, -2, or -3 or IgM which bindcomplement, can also be used in the presence of complement. In oneembodiment, ex vivo treatment of a population of cells comprising targetcells with a binding agent of the invention and appropriate effectorcells can be supplemented by the addition of complement or serumcontaining complement. Phagocytosis of target cells coated with abinding agent of the invention can be improved by binding of complementproteins. In another embodiment target cells coated with thecompositions of the invention can also be lysed by complement. In yetanother embodiment, the compositions of the invention do not activatecomplement.

The compositions of the invention can also be administered together withcomplement. Accordingly, within the scope of the invention arecompositions comprising antibodies, multispecific or bispecificmolecules and serum or complement. These compositions are advantageousin that the complement is located in close proximity to the antibodies,multispecific or bispecific molecules.

Alternatively, the antibodies, multispecific or bispecific molecules ofthe invention and the complement or serum can be administeredseparately. Binding of the compositions of the present invention totarget cells may cause translocation of the GT468 antigen-antibodycomplex into lipid rafts of the cell membrane. Such translocationcreates a high density of antigen-antibody complexes which mayefficiently activate and/or enhance CDC.

Also within the scope of the present invention are kits comprising theantibody compositions of the invention (e.g., antibodies andimmunoconjugates) and instructions for use. The kit can further containone or more additional reagents, such as an immunosuppressive reagent, acytotoxic agent or a radiotoxic agent, or one or more additionalantibodies of the invention (e.g., an antibody having a complementaryactivity).

Accordingly, patients treated with antibody compositions of theinvention can be additionally administered (prior to, simultaneouslywith, or following administration of a antibody of the invention) withanother therapeutic agent, such as a cytotoxic or radiotoxic agent,which enhances or augments the therapeutic effect of the antibodies ofthe invention.

In other embodiments, the subject can be additionally treated with anagent that modulates, e.g., enhances or inhibits, the expression oractivity of Fc-gamma or Fc-alpha receptors by, for example, treating thesubject with a cytokine. Preferred cytokines include granulocytecolony-stimulating factor (G-CSF), granulocyte-macrophagecolony-stimulating factor (GM

CSF), interferon-γ (IFN-γ), and tumor necrosis factor (TNF). Otherimportant agents for increasing the therapeutic efficacy of theantibodies and pharmaceutical compositions described herein areβ-glucans which are homopolysaccharides of branched glucose residues andare produced by a variety of plants and microorganisms, for example,bacteria, algae, fungi, yeast and grains. Fragments of β-glucansproduced by organisms may be also be used. Preferably, the β-glucan is apolymer of β(1,3) glucose wherein at least some of the backbone glucoseunits, e.g. 3-6% of the backbone glucose units, possess branches such asβ(1,6) branches.

In a particular embodiment, the invention provides methods for detectingthe presence of GT468 antigen in a sample, or measuring the amount ofGT468 antigen, comprising contacting the sample, and a control sample,with a antibody which specifically binds to GT468, under conditions thatallow for formation of a complex between the antibody or portion thereofand GT468. The formation of a complex is then detected, wherein adifference complex formation between the sample compared to the controlsample is indicative for the presence of GT468 antigen in the sample.

In still another embodiment, the invention provides a method fordetecting the presence or quantifying the amount of cells expressingGT468 and/or being characterized by association of GT468 with their cellsurface in vivo or in vitro. The method comprises (i) administering to asubject a composition of the invention conjugated to a detectablemarker; and (ii) exposing the subject to a means for detecting saiddetectable marker to identify areas containing cells expressing GT468and/or being characterized by association of GT468 with their cellsurface.

Methods as described above are useful, in particular, for diagnosingGT468-related diseases and/or the localization of GT468-related diseasessuch as cancer diseases. Preferably an amount of GT468 in a sample whichis higher than the amount of GT468 in a control sample is indicative forthe presence of a GT468-related disease in a subject, in particular ahuman, from which the sample is derived.

In yet another embodiment immunoconjugates of the invention can be usedto target compounds (e.g., therapeutic agents, labels, cytotoxins,radiotoxins immunosuppressants, etc.) to cells which have GT468associated with their surface by linking such compounds to the antibody.Thus, the invention also provides methods for localizing ex vivo or invitro cells expressing GT468 and/or being characterized by associationof GT468 with their cell surface, such as circulating tumor cells.

The present invention is further illustrated by the following exampleswhich are not be construed as limiting the scope of the invention.

EXAMPLES Example 1 Materials and Methods

The techniques and methods mentioned herein are carried out in a mannerknown per se and as described, for example, in Sambrook et al.,Molecular Cloning: A Laboratory Manual, 2nd Edition (1989) Cold SpringHarbor Laboratory Press, Cold Spring Harbor, N.Y., or as describedbelow. All methods including the use of kits and reagents are carriedout according to the manufacturers' information.

Tissues and Cell Lines

Recombinant DNA work was done with the official permission and accordingto the rules of the state government of Rheinland-Pfalz. Tissues wereobtained as human surplus materials during routine diagnostic ortherapeutic procedures and were stored at −80° C. until use. Breastcancer cell lines MCF-7 and BT549 were cultured in DMEM/10% FCS.

RNA-Isolation, RT-PCR and Real-Time RT-PCR

RNA extraction, first-strand cDNA synthesis, RT-PCR and real-time RT-PCRwere performed as previously described (Koslowski, M., Sahin, U., Huber,C. & Tureci, O. (2006) Hum. Mol. Genet. 15, 2392-2399). For end-pointanalysis GT468-specific oligonucleotides (sense 5′-AAA TTT GGC AGC TGCCTT CAC-3′; antisense 5′-TGA TGC CAC ATT CAG TAA CAC-3′, 60° C.annealing) were used in a 35 cycle RT-PCR. Real-time quantitativeexpression analysis was performed in triplicates in a 40 cycle RT-PCR.After normalization to HPRT (sense 5′-TGA CAC TGG CAA AAC AAT GCA-3′;antisense 5′-GGT CCT TTT CAC CAG CAA GCT-3′, 62° C. annealing) GT468transcripts in tumor samples were quantified relative to normal tissuesusing ΔΔCT calculation. Specificity of PCR reactions was confirmed bycloning and sequencing of amplification products from arbitrarilyselected samples.

Bioinformatics

For in silico cloning of trophoblast-specific molecules a data miningstrategy described in detail elsewhere was modified and adapted(Koslowski, M., Bell, C., Seitz, G., Lehr, H. A., Roemer, K.,Muntefering, H., Huber, C., Sahin, U. & Tureci, O. (2004) Cancer Res.64, 5988-5993; Koslowski, M., Tureci, O., Bell, C., Krause, P., Lehr, H.A., Brunner, J., Seitz, G., Nestle, F. O., Huber, C. & Sahin, U. (2002)Cancer Res. 62, 6750-6755; Koslowski, M., Sahin, U., Huber, C. & Tureci,O. (2006) Hum. Mol. Genet. 15, 2392-2399). Briefly, hierarchical keywordsearch of GenBank was combined with digital cDNA-library subtraction.

For keyword search nucleotide sequence files at GenBank were accessedfor genes annotated to be specifically expressed in placenta ortrophoblast tissue using the ENTREZ Search and Retrieval System(www.ncbi.nlm.nih.gov/Entrez). The sequence homology-searching programBLASTN (ncbi.nlm.nih.gov/blast) was run sequentially for each nucleotidesequence against all of the human nucleotide sequences to preventredundancies. As a second filter electronic Northern (eNorthern) wasperformed for all clones obtained by keyword search by BLAST search ofeach DNA sequences of interest against EST database at NCBI(www.ncbi.nlm.nih.gov/BLAST). It was taken into consideration thatseveral cDNA libraries in the public domain are not properly annotated(Scheurle, D., DeYoung, M. P., Binninger, D. M., Page, H., Jahanzeb, M.& Narayanan, R. (2000) Cancer Res. 60, 4037-4043).

For digital subtraction the cDNA xProfiler tool of the Cancer GenomeAnatomy Project at NCBI (cgap.nci.nih.gov/Tissues/xProfiler) was used,which compares gene expression between two pools (A and B) of cDNAlibraries where each pool can be either a single library or severallibraries. The search options for Pool A and Pool B were set to “Homosapiens” for Organism and “all EST libraries” for Library Group tosearch all cDNA libraries in dbEST. All cDNA libraries prepared fromplacenta and trophoblast tissue matching the search option settings wereassigned to Pool A excluding mixed tissue libraries. For Pool B all cDNAlibraries prepared from normal tissues except placenta, trophoblast,testis, ovary and whole body fetus were selected.

For analysis of the GT468 promotor region EMBOSS CpGPlot (Rice, P.,Longden, I. & Bleasby, A. (2000) Trends Genet. 16, 276-277) software wasused. Moreover, analysis of the GT468 protein sequence was conductedwith MEMSAT3 (Jones, D. T., Taylor, W. R. & Thornton, J. M. (1994)Biochemistry 33, 3038-3049), TMpred (Hofmann, K. & Stoffel, W. (1993)Biol. Chem. Hoppe-Seyler 374, 166), and GOR IV (Garnier, J., Osguthorpe,D. J. & Robson, B. (1978) J. Mol. Biol. 120, 97-120).

Antisera, Immunofluorescence and Immunochemistry

The polyclonal antiserum raised against as 117-127 of GT468 wasgenerated by a custom antibody service (Squarix, Marl, Germany).Immunohistochemistry was performed on tissue cyrosections using theVECTOR NovaRED Substrate Kit (Vector, Burlingame, Calif.) according tothe manufacturers instructions. For Western blot analysis 30 μg of totalprotein extracted from cells lyzed with Triton-X was used. Extracts werediluted in reducing sample buffer (Roth, Karlsruhe, Germany), subjectedto SDS-PAGE and subsequently electrotransferred onto PVDF membrane(Pall, East Hills, N.Y.). Immunostaining was performed with antibodiesreactive to pAKT (Cell Signaling, Danvers, Mass.), AKT (Cell Signaling,Danvers, Mass.), cyclin D1 (Santa Cruz Biotechnology, Santa Cruz,Calif.) and beta-Actin (Abeam, Cambridge, UK) followed by detection ofprimary antibody with horseradish-peroxidase conjugated goat anti-mouseand goat anti-rabbit secondary antibodies (Dako, Glostrup, Denmark).

siRNA Duplexes

The GT468 siRNA duplex (Qiagen, Hilden, Germany) (sense 5′-r(CCA UGA GAGUAG CCA GCA)dTdT-3′, antisense 5′-r(UUG CUG GCU ACU CUC AUG G)dAdG-3′)targeted nucleotides 670-690 of the GT468 mRNA sequence(NM_(—)021796.3). As control a scrambled siRNA duplex (sense 5′-r(UAACUG UAU AAU CGA CUA G)dTdT-5′, antisense 5′-r(CUA GUC GAU UAU ACA GUUA)dGdA-3′) was used. For GT468 silencing studies cells were transfectedwith 10 nM siRNA duplex using HiPerFect transfection reagent (Qiagen)according to the manufacturers instructions. All results were reproducedwith a second set of GT468 siRNA duplexes (sense 5′-r(GGU UCA GGA CAAAGU CCA A)dTdT-3′, antisense 5′-r(UUG GAC UUU GUC CUG AAC C)dGdG-3′)targeting nucleotides 342-362.

Cell Proliferation Analysis Following Transfection of siRNA

24 h after transfection with siRNA duplexes 1×10⁴ cells were culturedfor 48 h in medium supplemented with 10% FCS. Proliferation was analyzedby measuring the incorporation of BrdU into newly synthesized DNAstrands using the DELFIA cell proliferation Kit (Perkin Elmer, Boston,Mass.) according to the manufacturer's instructions on a Wallac Victor²multi-label counter (Perkin Elmer, Boston, Mass.).

Cell Cycle Analysis

Cells were cultured in medium supplemented with 10% FCS in varyingconcentrations. 72 h after transfection with siRNA duplexes cells wereharvested, EtOH-fixed, and stained with propidiumiodide prior toflowcytometric DNA content analysis. Cells in the different phases ofthe cell cycle were quantified using CellQuest™ Pro (BD, Franklin Lakes,N.J.) and FlowJo™ (Tree Star, Ashland, Oreg.) flowcytometric analysissoftware. Apoptotic cells were quantified by AnnexinV staining 48 h and72 h after siRNA transfection.

Cell Migration and In Vitro Invasion Assay

Cell migration assays were conducted in transwell chambers with 8.0 μmpore membranes (BD Biosciences, San Jose, Calif.) with cells cultured inserum-free medium for 12 h prior to experiments. For siRNA experimentscells were transferred to serum-free conditions 24 h after transfectionwith siRNA duplexes as described above. 4×10⁴ cells in 400 μl serum-freeculture medium were added to the upper chamber. The bottom chamberscontained 800 μl culture medium supplemented with 5% FCS aschemoattractant. 24 h later cells that had migrated to the bottom sideof the membrane were fixed in ice-cold methanol; membranes were excised,placed on microscope slides and mounted with Hoechst (Dako, Glostrup,Denmark) for fluorescence microscopy. Cells in five random visual fields(100× magnification) were counted for each membrane. All experimentswere done in triplicates. Effects on chemokinesis of cells were analyzedusing the same experimental setup with chemoattractant added to both theupper and lower chamber. For in vitro invasion assays the upper chamberswere prepared with 100 μl of Matrigel (BD Biosciences, San Jose, N.J.)diluted to 1 mg/ml in serum free medium. Chambers were incubated at 37°C. for 5 h for gelling.

Cell Proliferation Analysis Following Incubation with Antibodies

Endogenously GT468-expressing cancer cell lines BT-549, Caov-3, EFO-21,MCF-7, and MDA-MB-231 were incubated with hybridoma supernatant diluted1:2 in DMEM cell culture medium for 72 h. Proliferation was analyzed bymeasuring the incorporation of BrdU into newly synthesized DNA strandsusing the DELFIA cell proliferation Kit (Perkin Elmer) according to themanufacturer's instructions on a Wallac Victor2 multi-label counter(Perkin Elmer).

Alternatively, endogenously GT468-expressing cancer cell lines SK-BR-3and MCF-7, respectively, were incubated with HPLC-purified hybridomasupernatants diluted in DMEM cell culture medium for 72 h or 120 h atconcentrations as indicated. Proliferation was analyzed as describedabove.

Immunofluorescence Microscopy

In order to demonstrate presence of anti-GT468 antibodies in sera ofimmunized mice or binding of monoclonal antibodies to living cellsexpressing GT468, immunofluorescence microscopy analysis was used. CHOcells transfected with GT468-eGFP were grown in chamber slides understandard growth conditions in DMEM/F12 medium, supplemented with 10%fetal calf serum (FCS), 2 mM L-glutamine, 100 IU/ml penicillin and 100μg/ml streptomycin. Cells then were fixed with methanol orparaformaldehyde/0.1% Saponin. Cells were incubated with antibodiesagainst GT468 for 60 min. at 25° C. After washing, cells were incubatedwith an Alexa555-labelled anti-mouse IgG secondary antibody (MolecularProbes) under the same conditions.

GT468 Peptide-Specific ELISA

Microwell plates (Nunc) were coated for one hour at 37° C. with therelevant GT468 peptide (5 μg/ml). Blocking was performed with PBS 3% BSAovernight at 4° C. After washing three times with PBS, the plates wereloaded with hybridoma supernatants (diluted 1:5 or 1:10 in PBS 3% BSA,50 μl per well) and incubated for 1 h at room temperature (orbitalshaking at 90 rpm). Secondary antibody (HRPO-conjugated goat anti-mouseIgG, Jackson Immunoresearch) in PBS 3% BSA was added after washing threetimes with PBS, and incubated for 1 h at room temperature with orbitalshaking at 90 rpm. After a final washing step (three times with PBS),substrate solution consisting of 1.5 mM ABTS in 100 mM sodium acetate(pH 5.2) was added. Immediately before use, the substrate solution wassupplemented with 0.3 μl per ml of 30% H₂0₂. Absorption at 405 nm wasmeasured on a Tecan Safire Plate reader (Tecan) after 30-60 min.

Immunizations

In the production of the clones deposited under the accession no. DSMACC2822 (4E9-1H9), DSM ACC2826 (9B6-2A9), DSM ACC2824 (59D6-2F2), DSMACC2825 (61C11-2B5), DSM ACC2823 (78H11-1H6), Balb/c or C57/BL6 wereimmunized with KLH-coupled peptides. 50 μg of peptides with 50 μlMontanide ISA 50V as adjuvant were injected intraperitoneally (i.p.) ondays 1, 15, 45, and 86. The presence of antibodies directed againstGT468 in sera of mice was monitored by peptide-specific ELISA on days24, 57, and 92. Mice with detectable immune responses were boosted threedays prior to splenectomy for generation of monoclonal antibodies.

In all other cases, Balb/c or C57/BL6 mice were immunized with GT468pcDNA3.1 plasmid with PEI Mannose as adjuvant intramuscularly (i.m.) onday 1 and 15. Thereafter, 50 μg of peptides with 50 μl Montanide ISA 50Vas adjuvant (intraperitoneally) or 150 μg protein with incompleteFreund's adjuvant (IFA) (subcutaneously) were injected on days 30 and45. The presence of antibodies directed against GT468 in sera of micewas monitored by peptide-specific ELISA or CrELISA. Mice with detectableimmune responses were boosted three days prior to splenectomy forgeneration of monoclonal antibodies.

Generation of Hybridomas Producing Human Monoclonal Antibodies to GT468

Mouse splenocytes were isolated and fused with PEG to a mouse myelomacell line based on standard protocols. The resulting hybridomas werethen screened for production of immunoglobulins with GT468 specificityusing peptide-specific ELISA, GT468 CrELISA and CHO cells transfectedwith GT468-eGFP by IF.

Single cell suspensions of splenic lymphocytes from immunized mice werefused with P3X63Ag8U.1 nonsecreting mouse myeloma cells (ATCC, CRL 1597)in a 2:1 ratio using 50% PEG (Roche Diagnostics, CRL 738641). Cells wereplated at approximately 3×10⁴/well in flat bottom microtiter plates,followed by about two week incubation in selective medium containing 10%fetal bovine serum, 2% hybridoma fusion and cloning supplement (HFCS,Roche Diagnostics, CRL 1 363 735) plus 10 mM HEPES, 0.055 mM2-mercaptoethanol, 50 μg/ml gentamycin and 1×HAT (Sigma, CRL H0262).After 10 to 14 days individual wells were screened by peptide-specificELISA for anti-GT468 monoclonal antibodies. The antibody secretinghybridomas were replated, screened again and, if still positive foranti-GT468 monoclonal antibodies, were subcloned by limiting dilution.The stable subclones were then cultured in vitro to generate smallamounts of antibody in tissue culture medium for characterization. Atleast one clone from each hybridoma, which retained the reactivity ofparent cells (by ELISA and IF), was chosen.

Isotyping

For isotyping of hybridoma supernatants, IsoStrip Mouse MonoclonalAntibody Isotyping Kit (Roche, Cat. No. 1493027) was used as describedby the manufacturer.

CrELISA Procedure Using Crude Lysates of GT468 Expressing BacterialLysates

Preparation of the Antigen

E. coli XLOLR bacteria were transformed either with GT468 pQE plasmid orinsertless pQE (will be referred to as “reference”) and grown in LBmedium to A600 nm ˜0.35 E. Protein expression was induced with 2 mMIPTG, and cells were allowed to grow for an additional 4 h at 37° C.Proper induction of protein expression and its kinetics were monitoredby Coomassie gel analysis. Bacteria were spun down and resuspended in asmall volume of PBS pH 7.2 containing 0.2 mM protease inhibitorAEBSF-hydrochloride (AppliChem). Cells were placed on ice and disruptedby sonication (Branson Sonic Power A Smithkline). GT468 and referencelysates were diluted to a total protein concentration of 2 mg/ml in PBScontaining 0.2 mM AEBSF and 20% (v/v) glycerol. Aliquots wereshock-frozen in nitrogen and stored at −70° C. until use.

Conduction of the Enzyme-Linked Immunosorbent Assay

Before use, GT468, as well as the reference lysates, was diluted incoating buffer (100 mM HEPES, pH 7.2), then transferred to flat-bottomF96 Maxisorp microwell plates (50 μl/well, Nunc) and adsorbed for 2 h at37° C.

After antigen immobilization, plates were washed twice with washingbuffer (50 mM Tris, 150 mM sodium chloride, pH 7.2) containing 0.1%Tween 20, and subsequently twice without detergent. Fifty microlitershuman sera diluted 1:100 was added per well and incubated for 1 h on anorbital shaker at ambient temperature. In some experiments, human serawere pretreated before subjecting them to the assay.

Each individual serum sample was tested in duplicate in parallel onwells coated with GT468 or reference lysate. Plates were washed again asdescribed above and incubated for 1 h at room temperature with 50μl/well of secondary antibody (goat anti-human IgG-AP, Dianova) diluted1:5000 in 50 mM HEPES (pH 7.4) containing 3% (w/v) milk powder. Plateswere developed with 100 μl/well of substrate solution [2 mg4-nitrophenyl phosphate disodium salt hexahydrate (Merck) per mlALP-buffer (Roche Diagnostics, Mannheim, Germany)] for 30 min at roomtemperature, and absorbance values immediately read at 405 nm on amicroplate reader (Victor2 Wallac, Perkin-Elmer, Turku, Finland).

Flowcytometric Analysis

HEK293 cells transfected with GT468 pcDNA3.1 plasmid or insertlessplasmid (mock) were harvested, fixed with ice-cold methanol, and blockedwith PBS/10% FCS for 30 min. Cells were incubated with hybridomasupernatant for 1 h, washed twice with PBS/1 FCS for 10 min, andincubated with a goat anti-mouse Cy3 secondary antibody (JacksonImmunoResearch Laboratories).

Western Blots

Whole cell lysates of HEK293 cells transfected with GT468 pcDNA3.1plasmid or insertless plasmid (mock) were prepared using Triton-X basedlysis buffer (50 mM HEPES (pH 7.4), 10% (v/v) Glycerol, 1% (v/v) TritonX-100, 150 mM NaCl, 1.5 mM MgCl₂, 5 mM EDTA, 100 mM NaF). Extracts werediluted in reducing sample buffer (Roth), subjected to SDS-PAGE andsubsequently electrotransferred onto PVDF membrane (Pall).Immunostaining was performed with a polyclonal antibody reactive toGT468 (Koslowski et al. 2007) followed by detection of primary antibodywith horseradish-peroxidase conjugated goat anti-rabbit secondaryantibodies (Jackson ImmunoResearch Laboratories).

Example 2 GT468 is Aberrantly Activated and Highly Expressed in VariousTumors

To identify placenta-specific trophoblastic genes, a genome-wide datamining strategy was adapted, which we had originally developed for insilico identification of germ cell-specific molecules (Koslowski, M.,Bell, C., Seitz, G., Lehr, H. A., Roemer, K., Muntefering, H., Huber,C., Sahin, U. & Tureci, O. (2004) Cancer Res. 64, 5988-5993; Koslowski,M., Tureci, O., Bell, C., Krause, P., Lehr, H. A., Brunner, J., Seitz,G., Nestle, F. O., Huber, C. & Sahin, U. (2002) Cancer Res. 62,6750-6755; Koslowski, M., Sahin, U., Huber, C. & Tureci, O. (2006) Hum.Mol. Genet. 15, 2392-2399). In principle, hierarchical keyword search ofGenBank was combined with digital cDNA-library subtraction forprediction of authentically placenta-specific genes. GT468 wasidentified by this approach.

GT468 mRNA was investigated in a comprehensive set of normal andneoplastic tissue specimens by end-point RT-PCR and quantitativereal-time RT-PCR. It was confirmed that GT468 expression is confined toplacenta. In all other normal tissue specimens transcript amounts arebelow or just at the detection limit of highly sensitive RT-PCR (FIG.1A, B, C, Tab. 1). The only exception is testis, albeit with transcriptlevels 3 to 4 logs lower than those observed in placenta.

TABLE 1 Expression of GT468 in tissues and cell lines typed by end-pointRT-PCR GT468 expression Normal tissues Testis 2/3 Placenta 3/3 Brain 0/3Lung 0/3 Breast 0/3 Colon 0/3 Liver 0/3 Stomach 0/3 Kidney 0/3 Prostate0/3 Pancreas 0/3 Ovary 0/3 Spleen 0/3 Skin 0/2 Myocard 0/2 Endometrium0/3 rest. PBMCs 0/3 prolif. PBMCs 1/6 Small intestine 0/3 Thymus 0/2Adrenal gland 0/2 Cancerous tissues Breast cancer 44/62 Lung cancer21/50 Gastric cancer 18/31 Ovarian cancer 2/9 Hepatocellular carcinoma1/5 Cancer cell lines 22/40

In 38% (86/225) of primary tumor specimens across different cancer typesand 55% (22/40) of tumor cell lines, however, aberrant activation ofthis gene with otherwise tightly controlled transcription was found.Prevalence and transcript levels of GT468 were highest in breast cancerand breast cancer cell lines (FIG. 1A, B, C). 44 of 62 (82%) primarybreast cancer samples scored positive for GT468 expression (defined asat least 100-fold above background in non-trophoblastic normal tissues),with 24% (15/62) showing low (100-1000 fold), 40% (25/62) showingmoderate (1000-10.000 fold), and 17% (11/62) showing high (>10.000 fold)expression (FIG. 1B). Moreover, we found GT468 transcription in 21 of 50(42%) lung cancer samples as well as in gastric and ovarian cancer (Tab.1). Induction of GT468 did not correlate with histological subtype,tumor stage or tumor grade.

Example 3 GT468 is Located on the Surface of Cancer Cells and isAccessible for Antibodies

A polyclonal rabbit antibody (rabbit anti-GT468/C-term) against aGT468-specific peptide epitope (aa 117-127 of SEQ ID NO: 2) was raised.Specificity of the antibody was verified by gene silencing of GT468using small interfering RNA (siRNA). To exclude siRNA off targetactivity experiments were conducted with two sets of GT468 specificsiRNA duplexes, a scrambled non-silencing oligonucleotide andnon-transfected cells. By transfecting breast cancer cell lines MCF-7and BT-549 with these siRNA duplexes a stable and reproducible reductionof constitutive GT468 mRNA expression by 80-90% compared to controls wasachieved (FIG. 1D). Consistent with this observation, the 26 kDa band,detected in accordance with the predicted size of GT468 in Western blot,nearly completely disappeared in both cell lines (FIG. 1E), proving bothrobust knockdown of GT468 protein expression and specificity of theantibody.

Western Blot staining of GT468 protein in primary human tissue sampleswith rabbit anti-GT468/C-term confirmed that this gene is detectable inbreast cancer specimens in levels comparable to placenta as the onlynormal tissue it is expressed in (FIG. 1F). Immunohistochemistry withrabbit anti-GT468/C-term on human breast tumor sections showed specificimmunoreactivity in specimens typed positive for GT468 mRNA expressionby RT-PCR. Staining was confined to the neoplastic cell population,whereas adjacent stromal and non-neoplastic epithelial cells as well aspatient matched normal tissues were not reactive (FIG. 1G).Immunostaining of tumor cells was accentuated at the plasma membrane,providing evidence that GT468 is a cell surface protein.

In silico analysis of the topology of the GT468 protein sequencepredicted a hydrophobic domain spanning as 5 to 22 followed by a largeextracellular domain constituted by aa 23 to 212. Amino acids 29 to 119of the extracellular part of GT468 represent a truncated zona pellucida(ZP) domain. The ZP domain is found in a variety of extracellularlyexposed receptor-like proteins, including TGF-beta receptor type III,uromodulin, glycoprotein GP2 as well as the sperm receptors ZP2 and ZP3(Bork, P. & Sander, C. (1992) FEBS Lett 300, 237-240) and is involved inpolymerization (Jovine, L., Janssen, W. G., Litscher, E. S. & Wassarman,P. M. (2006) BMC. Biochem. 7, 11). The subcellular localization ofconstitutively expressed GT468 was assessed by immunofluorescencemicroscopy of MCF-7 and BT-549 breast cancer cells stained with rabbitanti-GT468/C-term, which has its epitope (aa 117 to 127) in thepresumably extracellular part of the protein. Both cell lines displayeddistinct staining at the cell membrane (FIG. 2A). Loss of signal uponsiRNA-induced knockdown of GT468 expression confirmed the specificity ofthe staining. Most importantly, specific membrane staining was observednot only on methanol-fixed but also non-fixed, native cells (FIG. 2B)implying that the epitope of the antibody is accessible withoutpermeabilization of the cell membrane and thus supporting the predictedtopology with extracellular localization of the carboxy-terminus.

Example 4 siRNA Induced Gene Silencing of GT468 Inhibits Motility,Migration and Invasion and Blocks Proliferation of Cancer Cells

To determine the biological significance of GT468 in tumor cells theeffects of its siRNA induced gene silencing on essential cell functionswere studied.

First, performance of breast cancer cell lines MCF-7 and BT-549 intranswell migration assays was investigated. Baseline motility(chemokinesis) of both cell lines assessed by adding 5% FCS aschemoattractant to both the upper and lower chamber of the system wassubstantially inhibited by GT468 specific siRNA duplexes (FIG. 3A).Consequently, we also observed a marked reduction of the directionalchemotactic migratory capacity of the cells (FIG. 3B). Moreover,chemoinvasion activity of cells was profoundly affected by GT468 siRNAtreatment, as cells were not able to migrate along chemoattractantgradients by breaking through a barrier of Matrigel (FIG. 3C).

Next, it was observed that tumor cell proliferation as measured by BrdUincorporation into DNA was reduced by 80-90% in both cell lines by GT468specific siRNA duplexes (FIG. 4A). Cell cycle analysis revealed adistinct G1/S arrest in the cells transfected with GT468 siRNA as theunderlying cause for the proliferation block (FIG. 4B). Vitality of thecells was not affected and staining for Annexin V gave no indicationsfor apoptotic cell death (FIG. 4C).

Example 5 Treatment of Cancer Cells with Anti-GT468 Antibodies InhibitsCell Growth

We measured proliferation of MCF-7 and BT-549 cells incubated withrabbit anti-GT468/C-term and a non-reactive control antibody. Targetingof GT468 resulted in efficient inhibition of proliferation of both celllines in a concentration-dependent manner (FIG. 5).

Example 6 Downstream Effects of siRNA-Induced Silencing andAntibody-Induced Functional Antagonization of GT468

Proliferation and cell cycle progression in eukaryotic cells is governedby cyclins and cyclin dependent kinases (CDKs). Individual cyclins actat different phases of the cell cycle by stimulating the activities of aseries of CDKs. Restriction point control is mediated by cyclin D- andE-dependent kinase families (Morgan, D. O. (1997) Annu. Rev. Cell Dev.Biol. 13, 261-291; Sherr, C. J. (2000) Cancer Res. 60, 3689-3695). Toinvestigate whether GT468 silencing induces the observed cell cycledysregulation via alteration of cyclin expression, expression of cyclinsD1, D2, D3 and cyclin E in MCF-7 and BT-549 breast cancer cells treatedwith GT468 siRNA was determined.

Interestingly, a significant reduction of cyclin D1 transcripts asmeasured by real-time PCR (FIG. 6A) as well as cyclin D1 protein levelsin Western blot (FIG. 6B) occurred as a consequence of GT468 knockdown.No change in transcription levels was observed for the other cyclinsanalyzed.

Cyclin D1 is known to be a major regulator of the G1 to S progression ofthe cell cycle. Interestingly, in the tumorigenesis of sporadic breastcancer, overexpression of cyclin D1 is regarded as an early event(Caldon, C. E., Daly, R. J., Sutherland, R. L. & Musgrove, E. A. (2006)J. Cell Biochem. 97, 261-274; Sutherland, R. L. & Musgrove, E. A. (2004)J. Mammary. Gland. Biol. Neoplasia. 9, 95-104). D-type cyclins areunstable, and their induction, synthesis, and assembly with theircatalytic partners all depend on persistent mitogenic signaling. Thus,D-type cyclins act as growth factor sensors, forming active kinases inresponse to extracellular factors (Sutherland, R. L. & Musgrove, E. A.(2004) J. Mammary. Gland Biol. Neoplasia. 9, 95-104; Sherr, C. J. (1993)Cell 73, 1059-1065). In breast cancer it has been shown, that cyclin D1expression is controlled via a phosphatidylinositol 3-kinase(PI3K)/AKT-dependent pathway (Sutherland, R. L. & Musgrove, E. A. (2004)J. Mammary. Gland. Biol. Neoplasia. 9, 95-104; D'Amico, M., Hulit, J.,Amanatullah, D. F., Zafonte, B. T., Albanese, C., Bouzahzah, B., Fu, M.,Augenlicht, L. H., Donehower, L. A., Takemaru, K. et al. (2000) J. Biol.Chem. 275, 32649-32657; Muise-Helmericks, R. C., Grimes, H. L.,Bellacosa, A., Malstrom, S. E., Tsichlis, P. N. & Rosen, N. (1998) J.Biol. Chem. 273, 29864-29872). AKT inactivates glycogen synthasekinase-3beta (GSK-3β), thereby increasing cyclin D1 transcription aswell as its proteolytic turnover and its protein levels in the nucleus(Sutherland, R. L. & Musgrove, E. A. (2004) J. Mammary. Gland. Biol.Neoplasia. 9, 95-104, Diehl, J. A., Cheng, M., Roussel, M. F. & Sherr,C. J. (1998) Genes Dev. 12, 3499-3511; Radu, A., Neubauer, V., Akagi,T., Hanafusa, H. & Georgescu, M. M. (2003) Mol. Cell Biol. 23,6139-6149). In addition, the AKT pathway is an important regulator ofcancer cell motility and migration (Sutherland, R. L. & Musgrove, E. A.(2004) J. Mammary. Gland. Biol. Neoplasia. 9, 95-104, Cantley, L. C.(2002) Science 296, 1655-1657; Luo, J., Manning, B. D. & Cantley, L. C.(2003) Cancer Cell 4, 257-262), two other cell functions in which GT468is apparently involved. This prompted us to analyze whether GT468 has animpact on the regulation of AKT kinase in MCF-7 and BT-549 cells.

Constitutive phosphorylation and hyperactivation of AKT consecutive toPI3K overactivation is frequently observed in tumor cells.Quantification of levels of Ser473 phosphorylation of AKT (pAKT)subsequent to silencing of GT468 by siRNA technology and its functionalantagonizing with antibody anti-GT468/C-term both resulted in a markedreduction of pAKT levels in particular in MCF-7 cells (FIG. 6C),suggesting that AKT kinase activation is involved in execution ofdown-stream effects of GT468. Interestingly, downregulation of pAKT wasless prominent in BT-549 cells, which lack PTEN and therefore have ahigher level of PI3K overactivation.

Example 7 GT468-Specific Monoclonal Antibodies

Peptides having sequences according to SEQ ID NOs: 3-10 were used forgeneration of hybridomas producing monoclonal antibodies. For example,immunization using the peptide of SEQ ID NO: 3 gave hybridomas 4E9-1H9and 9B6-2A9, immunization using the peptide of SEQ ID NO: 4 gavehybridoma 59D6-2F2, and immunization using the peptide of SEQ ID NO: 6gave hybridomas 61C11-2B5 and 78H11-1H6.

A peptide-specific ELISA was performed to ensure specific binding of themonoclonal antibodies. Hybridoma supernatants were tested in 1:5 or 1:10dilution against the respective peptide used for immunization of mice.As control all hybridoma supernatants were tested against two irrelevantpeptides. All monoclonal antibodies reacted specifically only with therespective peptide used for immunization of mice (FIG. 7).

Specific binding of the monoclonal antibodies to full-length GT468protein was analyzed by immunofluorescence (IF) microscopy. 24 h aftertransfection of a GT468-eGFP fusion construct CHO cells were stainedwith hybridoma supernatants (1:5 dilution). Merging of the eGFP signaland the signal of secondary anti-mouse antibody (Alexa555) showedstaining only of the GT468-eGFP transfected cells whereasnon-transfected cells were negative (FIG. 8).

To analyze the impact of the monoclonal antibodies binding to GT468 onproliferation of cancer cells, endogenously GT468-expressing cancer celllines BT-549, Caov-3, EFO-21, MCF-7, and MDA-MB-231 were incubated withhybridoma supernatants (1:2 dilution) for 72 h. Proliferation of cellswas measured by BrdU incorporation into DNA. Whereas monoclonal antibody4E9 1H9 did not alter the proliferation of the cells at theconcentration used, antibodies 9B6 2A9 and 59D6 2F2 clearly reduced theproliferation of all cancer cell lines analyzed (FIG. 9).

Thus, it was shown that monoclonal antibodies can be produced whichselectively target GT468 expressed by cells. Furthermore, it was shownthat monoclonal antibodies to GT468 can be produced which inhibitproliferation of cancer cells expressing GT468.

Example 8 GT468-Specific Monoclonal Antibodies Obtained fromImmunization with GT468 pcDNA3.1 Plasmid Followed by Peptide/ProteinInjection

Twofold intramuscular immunization using GT468 DNA followed by twofoldsubcutaneous administration of recombinant GT468 protein resulted inhybridomas 22-1A-1, 22-2A-1, 22-9B-1, 23-33A-1 and 23-19A-1. Twofoldintramuscular immunization using GT468 DNA followed by twofoldintraperitoneal administration of the peptide according to SEQ ID NO: 10resulted in hybridoma F11#33F7D12. Twofold intramuscular immunizationusing GT468 DNA followed by twofold intraperitoneal administration ofthe peptide according to SEQ ID NO: 3 resulted in hybridomas 4A12 2D41A10 and 4E9 1D12 2D4.

The following table lists the antibodies obtained and their isotypes.

TABLE 2 Monoclonal antibodies obtained by immunization with GT468 DNAfollowed by injection of peptide/protein Hybridoma Isotype 22-1A-1 IgG2b22-2A-1 IgG2b 22-9B-1 IgG2a 23-33A-1 IgG1 23-19A-1 IgG1 F11#33F7D12 IgG14A12 2D4 1A10 IgG1 4E9 1D12 2D4 IgG3

A crude-lysate (CrELISA) was performed to ensure specific binding of themonoclonal antibodies from hybridomas 22-1A-1, 22-2A-1, 22-9B-1,23-33A-1, and 23-19A-1. Hybridoma supernatants were tested against thelysate of E. coli transformed with GT468 pQE expression vector. Ascontrol, hybridoma supernatants were tested on lysate of E. colitransformed with insertless (mock) pQE plasmid. All monoclonalantibodies reacted specifically only with the specific GT468 lysate(FIG. 10A).

A peptide-specific ELISA was performed to ensure specific binding of themonoclonal antibodies from hybridomas F11#33F7D12, 4A12 2D4 1A10, and4E9 1D12 2D4. Hybridoma supernatants were tested against the respectivepeptide used for immunization of mice. As control, hybridomasupernatants were tested against an irrelevant peptide. The monoclonalantibodies reacted specifically only with the respective peptide usedfor immunization of mice (FIG. 10 B).

Specific binding of the monoclonal antibodies to full-length GT468protein was analyzed by flowcytometric analysis as described herein. Forflowcytometric analysis of monoclonal antibody 4E9 1D12 2D4 transientlytransfected HEK cells with a transfection rate of approx. 40% were used.All hybridoma supernatants showed specific staining of GT468 transfectedcells, whereas no staining was observed on mock transfected cells (FIG.11).

Specific binding of the monoclonal antibodies to full-length GT468protein was analyzed by Western blot. All hybridoma supernatants showedspecific reactivity with lysates of HEK293 cells transfected with GT468pcDNA3.1 expression plasmid, whereas lysates of mock transfected cellsshowed no signal (FIG. 12; The faint signal of hybridoma supernatant23-33A-1 in the mock lysate is believed to result from spillover of theHEK GT468 lysate).

A peptide ELISA was performed to identify epitopes in the GT468 proteinto which the monoclonal antibodies bind to. The complete GT468 proteinsequence was synthesized as set of 51 overlapping peptides (15mers) withan overlap of 11 aa. All hybridoma supernatants were tested in ELISA forspecific binding to these peptides. As control, an irrelevant peptidewas used. All supernatants showed specific binding to GT468 peptides.Hybridoma supernatants 22-1A-1, 23-33A-1, and 23-19A-1 each showedbinding to two overlapping peptides implying reactivity to a linearepitope of GT468. The binding patterns of 22-2A-1 and 22-9B-1 were morecomplex, implying reactivity to conformational epitopes of the GT468protein.

To analyze the impact of the monoclonal antibodies binding to GT468 onproliferation of cancer cells, endogenously GT468-expressing cancer celllines SK-BR-3 (4A12 2D4 1A10) or MCF-7 (4E9 1D12 2D4) were incubatedwith purified hybridoma supernatants for 72 h or 120 h at theconcentrations indicated in FIG. 14. Proliferation of cells was measuredby BrdU incorporation into DNA. Whereas the irrelevant controlmonoclonal antibody did not alter the proliferation of the cells,monoclonal antibodies 4A12 2D4 1A10 and 4E9 1D12 2D4 clearly reduced theproliferation of cells in a concentration dependent manner (FIG. 14).

The invention claimed is:
 1. An isolated antibody having the ability ofbinding to an epitope located within the extracellular domain of theprotein comprising the amino acid sequence of SEQ ID NO: 2 and mediatinginhibition of proliferation of cells, wherein said cells express aprotein comprising the amino acid sequence of SEQ ID NO: 2 and/or arecharacterized by association of a protein comprising the amino acidsequence of SEQ ID NO: 2 with their cell surface.
 2. The isolatedantibody of claim 1 wherein said inhibition of proliferation of saidcells is induced by binding of said antibody to the protein.
 3. Theisolated antibody of claim 1 wherein said cells are cancer cells.
 4. Theisolated antibody of claim 3, wherein said cancer cells are selectedfrom the group consisting of tumorigenic breast, lung, gastric, ovarian,liver, colon, pancreatic, esophageal, head-neck, renal, prostate andhepatocellular cancer cells.
 5. The isolated antibody of claim 1 whichis a monoclonal, chimeric, human or humanized antibody, or anantigen-binding fragment of an antibody.
 6. The isolated antibody ofclaim 1, selected from the group consisting of an IgG1, an IgG2, anIgG3, an IgG4, an IgM, an IgA1, an IgA2, a secretory IgA, an IgD, and anIgE antibody.
 7. The isolated antibody of claim 6 selected from thegroup consisting of an IgG2a and an IgG2b antibody.
 8. The isolatedantibody of claim 1 wherein the amino acid sequence of said proteinconsists of the amino acid sequence according to SEQ ID NO:
 2. 9. Theisolated antibody of claim 1 wherein the antibody binds specifically toa protein comprising the amino acid sequence of SEQ ID NO:
 2. 10. Theisolated antibody of claim 1 which binds to a conformational epitope ofa protein comprising the amino acid sequence of SEQ ID NO: 2 present onthe surface of living cells.
 11. The isolated antibody of claim 1wherein said protein comprising the amino acid sequence of SEQ ID NO: 2is expressed on the surface of said cells.
 12. The isolated antibody ofclaim 1 which is obtainable by a method comprising the step ofimmunizing an animal with a protein or peptide having an amino acidsequence selected from the group consisting of SEQ ID NO: 2-10 and35-79, or an immunogenic fragment or derivative thereof, or a nucleicacid or host cell expressing said protein or peptide, or immunogenicfragment or derivative thereof.
 13. An isolated antibody produced by aclone deposited under the accession no. DSM ACC2826 (9B6-2A9), DSMACC2824 (59D6-2F2), DSM ACC2823 (78H11-1H6), DSM ACC2895 (22-1A-1), DSMACC2893 (22-2A-1), DSM ACC2896 (22-9B-1), DSM ACC2897 (23-33A-1), DSMACC2891 (23-19A-1), DSM ACC2892 (4A12 2D4 1A10), or DSM ACC2898 (4E91D12 2D4).
 14. A hybridoma capable of producing the antibody of claim 1.15. A hybridoma deposited under the accession no. DSM ACC2826 (9B6-2A9),DSM ACC2824 (59D6-2F2), DSM ACC2823 (78H11-1H6), DSM ACC2895 (22-1A-1),DSM ACC2893 (22-2A-1), DSM ACC2896 (22-9B-1), DSM ACC2897 (23-33A-1),DSM ACC2891 (23-19A-1), DSM ACC2892 (4A12 2D4 1A10), or DSM ACC2898 (4E91D12 2D4).
 16. A conjugate comprising an antibody of claim 1, coupled toa therapeutic agent.
 17. The conjugate of claim 16, wherein thetherapeutic agent is a toxin, a radioisotope, a drug or a cytotoxicagent.
 18. A conjugate comprising an antibody of claim 13, coupled to atherapeutic agent.
 19. The conjugate of claim 18, wherein thetherapeutic agent is a toxin, a radioisotope, a drug or a cytotoxicagent.
 20. A pharmaceutical composition comprising an antibody of claim1, and a pharmaceutically acceptable carrier.
 21. A pharmaceuticalcomposition comprising an antibody of claim 13, and a pharmaceuticallyacceptable carrier.
 22. A pharmaceutical composition comprising aconjugate of claim 16, and a pharmaceutically acceptable carrier.
 23. Apharmaceutical composition comprising a conjugate of claim 18, and apharmaceutically acceptable carrier.